You are using MS-Access as the database, I presume?
We had terrible trouble when we started using TD as we used this setup for 4/5 people.
We lost/corrupted a day's data (some data was gone altogether, some tests were appearing under the wrong subjects, some steps under the wrong tests etc).
I said, "This is an Access problem - its not scaleable, we have to change".
I was overruled by people who said they had seen Access supporting 25/30 people, so we started from scratch again with Access. (Turned out that the BDE engine TD relies on puts FAR more strain on Access than the average client/server user).
Another day went by and exactly the same loss/corruption occurred - they listened second time around!
So, we moved to using Oracle on Solaris and never had a moment's trouble with it again. (I'd imagine SQL Server would be similar).
You have to use a proper database for this task - Access is a toy...
QUALITY . . . is like buying oats. If you want nice, clean, fresh oats, you must pay a fair price.
However, if you can be satisfied with oats that have already been through the horse . . . that comes a little cheaper.