Integration works but kills IIS

I have a couple of issues with a site. They have Sage 300 v6.0a. They are also running Sage CRM 7.1SP2 integrated. They've had Sage 300 for a long time and CRM is new for them.

Initially when CRM was installed, the sync was set up and the tables synched without a problem. However, if you created a record in CRM and promoted to vendor or customer, it was fine. If you created one in 300 and let it sync, it failed. What it does is to create a blank company record. Literally nothing in it. I followed KB 24047 and it seems to have worked on the server but the clients still have a problem.

Recently I now get an issue that when I promote a company to Accpac from CRM, it kills off the webserver and boots everyone out of CRM. It creates the record in Accpac and once it is created, I can edit from either system and the change is synched across. I followed a KB article about this problem and tried everything on it but it still fails.

Any help would be appreciated.