Has anyone seen an update to this issue? I do not see a resolution. I have a client on Sage 2015, CRM 7.3 and getting the illegal access attempt message when in CRM creating a new quote from an opportunity.

I did not see an response here. Sage Knowledgebase article 46155 has a number of suggestions which might be helpful if you are still running into this issue with newer Sage 100 and Sage CRM installations.

Error: "Illegal Access Attempt" in CRM when clicking on Sage 100 ERP links.
Products: Sage 100, CRM

Description: In Sage CRM, clicking on Sage 100 ERP related links such as Maintain Relationship, Customer Maintenance, New - Order, and/or New - Quote, etc. may display error message "Illegal Access Attempt" instead of launching the task selected.

Backup your Sage 100 and CRM Data.

Resolution:

Check Sage 100 ERP CRM Server Options and Company Options settings:
Check the Integration Server Name and Integration Server Port ID in CRM Server Options in Sage 100 ERP (Customer Relationship Management, Main, CRM Server Options).
Using a SQL query, check the MAS_CRMServerOptions table settings in the CRM database
Select * from MAS_CRMServerOptions
Check the MAS_IntegrationEngineServer and MAS_IntegrationEnginePort values as well as the MAS_SageCRMInstanceID (this should match the correct InstanceID within Sage 100 ERP CRM Server Options).
If using Sage 100 ERP Advanced or Premium versions then the MAS_ServerName and MAS_ServerPort should also be populated with the correct Application Server information.
If these appear incorrect or blank, change any setting in Sage 100 ERP CRM Server Options screen (Customer Relationship Management, Main, CRM Server Options) and select Accept to see if this will update the SQL database MAS_CRMServerOptions table (you will need to run the query above again to confirm)
Change back the value you changed in CRM Server Options after your test and click Accept
Select Load Sage CRM Data in CRM Server Options to confirm that communication is working

Check Sage 100 ERP Company settings:
Use CRM Company Options in Sage 100 ERP (Customer Relationship Management, Main, Company Options) to check the settings in Sage 100 ERP and confirm they are correct
Run SQL query in CRM database: Select * from MAS_Company
Compare the mascom_CompanyName, macom_MAS_CompanyKey and mascom_MAS_CompanyCode values against the correct settings in Sage 100 ERP.
Use Data File Display and Maintenance to confirm the CompanyKey for the appropriate company in ...\MAS90\MAS_SYSTEM\SY_Company.

Check the CU Tables in Sage 100 ERP:
Use Data File Display and Maintenance to check the CU tables: (located in ...\MAS90\MAS_SYSTEM) CU_CRMServerOptions, CU_MAS_Company, CU_Options and CU_Company to compare these values with the SQL tables and Sage 100 ERP CRM Server Options and Company Options as well as the Sage 100 ERP company code and key. Damaged CU tables may need to be repaired by doing a Rebuild CRM within Sage 100 ERP (both Sage 100 ERP and Sage CRM database must be backed up before using Rebuild CRM).

Customization:
The Create Script is missing or incomplete due to customization of Company screen in CRM:
Within CRM check the Create Script: Customization, Company, Screens, CompanyBoxLong, Company Name.
Modifying the following can damage the link between SageCRM and Sage 100 ERP or cause the links to work improperly: CompanyBoxLong, PersonBoxLong, AddressBoxLong, FinancialDetailsBox, OrderFilterBox, OrderSummary, QuoteFilterBox, QuoteSummary, LineItemsSummary, LineItemGrid, SystemMenu (Activity), CompanyTabInquiry, Orders/Quotes, OpportunityWebPicker

Workflow Customization: Changes may need to be un-done or restore done to undo changes

Internet Browser:
Confirm the Internet Browser being used is compatible with CRM in the CRM Software Support Matrix for the installed version of Sage CRM. CRM Software Support Matrix is available in the CRM Community web site.
If using Internet Explorer, try enabling or disabling Compatibility View and try again (please refer to the CRM Software Support Matrix for information for supported browsers for that specific version of Sage CRM)

Sage 100 Integration Engine service:
Run Sage 100 Integration Engine on the Sage 100 server as an application rather than a service (see Related Resources) - it is possible that Windows server cannot launch the task when running as a service
It is possible that the Sage 100 Integration Engine can get corrupted, manually uninstall and reinstall Sage 100 Integration Engine (see Related Resources).

Firewall or UAC blocking request:
Temporarily turn off the Windows Firewall on Sage 100, SQL, and/or CRM Servers
If this allows connection, you may need to set up Inbound/Outbound Rules for the Sage 100 Integration Engine port (default is 8888) or SQL instance TCP/IP port (default is 1433)
If still no connection, you can temporarily disable User Account Controls settings (UAC) on the servers or workstation receiving the error - see Related Resources

I did not see an response here. Sage Knowledgebase article 46155 has a number of suggestions which might be helpful if you are still running into this issue with newer Sage 100 and Sage CRM installations.

Error: "Illegal Access Attempt" in CRM when clicking on Sage 100 ERP links.
Products: Sage 100, CRM

Description: In Sage CRM, clicking on Sage 100 ERP related links such as Maintain Relationship, Customer Maintenance, New - Order, and/or New - Quote, etc. may display error message "Illegal Access Attempt" instead of launching the task selected.

Backup your Sage 100 and CRM Data.

Resolution:

Check Sage 100 ERP CRM Server Options and Company Options settings:
Check the Integration Server Name and Integration Server Port ID in CRM Server Options in Sage 100 ERP (Customer Relationship Management, Main, CRM Server Options).
Using a SQL query, check the MAS_CRMServerOptions table settings in the CRM database
Select * from MAS_CRMServerOptions
Check the MAS_IntegrationEngineServer and MAS_IntegrationEnginePort values as well as the MAS_SageCRMInstanceID (this should match the correct InstanceID within Sage 100 ERP CRM Server Options).
If using Sage 100 ERP Advanced or Premium versions then the MAS_ServerName and MAS_ServerPort should also be populated with the correct Application Server information.
If these appear incorrect or blank, change any setting in Sage 100 ERP CRM Server Options screen (Customer Relationship Management, Main, CRM Server Options) and select Accept to see if this will update the SQL database MAS_CRMServerOptions table (you will need to run the query above again to confirm)
Change back the value you changed in CRM Server Options after your test and click Accept
Select Load Sage CRM Data in CRM Server Options to confirm that communication is working

Check Sage 100 ERP Company settings:
Use CRM Company Options in Sage 100 ERP (Customer Relationship Management, Main, Company Options) to check the settings in Sage 100 ERP and confirm they are correct
Run SQL query in CRM database: Select * from MAS_Company
Compare the mascom_CompanyName, macom_MAS_CompanyKey and mascom_MAS_CompanyCode values against the correct settings in Sage 100 ERP.
Use Data File Display and Maintenance to confirm the CompanyKey for the appropriate company in ...\MAS90\MAS_SYSTEM\SY_Company.

Check the CU Tables in Sage 100 ERP:
Use Data File Display and Maintenance to check the CU tables: (located in ...\MAS90\MAS_SYSTEM) CU_CRMServerOptions, CU_MAS_Company, CU_Options and CU_Company to compare these values with the SQL tables and Sage 100 ERP CRM Server Options and Company Options as well as the Sage 100 ERP company code and key. Damaged CU tables may need to be repaired by doing a Rebuild CRM within Sage 100 ERP (both Sage 100 ERP and Sage CRM database must be backed up before using Rebuild CRM).

Customization:
The Create Script is missing or incomplete due to customization of Company screen in CRM:
Within CRM check the Create Script: Customization, Company, Screens, CompanyBoxLong, Company Name.
Modifying the following can damage the link between SageCRM and Sage 100 ERP or cause the links to work improperly: CompanyBoxLong, PersonBoxLong, AddressBoxLong, FinancialDetailsBox, OrderFilterBox, OrderSummary, QuoteFilterBox, QuoteSummary, LineItemsSummary, LineItemGrid, SystemMenu (Activity), CompanyTabInquiry, Orders/Quotes, OpportunityWebPicker

Workflow Customization: Changes may need to be un-done or restore done to undo changes

Internet Browser:
Confirm the Internet Browser being used is compatible with CRM in the CRM Software Support Matrix for the installed version of Sage CRM. CRM Software Support Matrix is available in the CRM Community web site.
If using Internet Explorer, try enabling or disabling Compatibility View and try again (please refer to the CRM Software Support Matrix for information for supported browsers for that specific version of Sage CRM)

Sage 100 Integration Engine service:
Run Sage 100 Integration Engine on the Sage 100 server as an application rather than a service (see Related Resources) - it is possible that Windows server cannot launch the task when running as a service
It is possible that the Sage 100 Integration Engine can get corrupted, manually uninstall and reinstall Sage 100 Integration Engine (see Related Resources).

Firewall or UAC blocking request:
Temporarily turn off the Windows Firewall on Sage 100, SQL, and/or CRM Servers
If this allows connection, you may need to set up Inbound/Outbound Rules for the Sage 100 Integration Engine port (default is 8888) or SQL instance TCP/IP port (default is 1433)
If still no connection, you can temporarily disable User Account Controls settings (UAC) on the servers or workstation receiving the error - see Related Resources