This sounds like there could be a serious error within your data file. I would suggest a phone call to Support tomorrow. Yes, a Saturday call as they are open in the morning on Saturdays for things like this. They can connect directly to your computer to try to trouble shoot the issue through searching the various logs of activity. You may have to send the data file to them to repair, just be prepared. Hopefully you are on a service plan.

Having the exact same problem. Posted a question with details asking for help but it isn't being allowed I presume because I'm new but the reason I got was that it was deemed abusive SPAM.

Anyway, after working on this all day I found that the problem seems to be related to historical data -- the first thing you need to do is check your DBvalitaor log -- to find the log to the documents directory and you'll see a directory called Simply and inside that a directory called DBvalitor -- inside that will be some numbered files. These are just text files so you'd open them in any text editor (Notepad)

The format of the file should be Begin and a description of what was being validated followed by End and the same description of what was being validated. If there are any lines between Begin and End then something unexpected happened. If the problem is like mine those errors will be on the last check which is for Historical Data.

Unfortunately, I have not yet found a solution. Calling support was not helpful but you might as well try as you might get a more helpful response. If you do could you report back with what they told you.

I believe this is a pretty serious problem but I did find other instances of people reporting this so we're not the only two. Some people were able to resolve this but their solutions did not work for me. I suspect that the only way to fix this is going to be to manually repair the database. I'm going to try to do that on the weekend using a backup.

Try to connect with Sage Support. Yes, they are busy and the wait time is lengthy. You can try telephone or chat from within Sage 50. I had a similar problem one year ago and once the support person was talking with me it took only a few minutes to correct. Support connected directly verified the error logs and then did a database rebuild. This latter part took the longest but still a lot less time than rebuilding the database manually. This database is very complex with many tables that must all connect or the whole thing will crash. 

The wait time isn't the problem so much as after contacting support twice I'm not confident that the people they have working there are competent. I'm going to try again on Monday and hopefully, there is a tier 2 support level I can get passed on to because I have honestly never experienced support as useless as what I got from Sage yesterday.