I had the same problem, mine seemed pretty consistent when closing windows or files. Sometimes with saving, sometimes without. I worked around it by always saving before closing.
I called GTAC and got a big time run-around because I didn't have an optimal system off the special list. Terribly disappointing way to treat a customer.
I am currently on 10.0.3.5. I didn't make a direct link between the installation of that version and the problems, but they did appear around that time. My problem is more intermittent (it doesn't happen all the time, seems close to 50% of the time I close a file).
Curious to see what came of this as we are experiencing the same issue and you sent a private message..
Were you able to find a root cause of this issue? If so, could you please share it?
Having matched the error in Steve's syslog with an existing, closed PR, I suggested that he install a maintenance pack for his current version in which the PR's problem was fixed.
If you're experiencing similar problems, please open an IR with GTAC and provide any syslogs from those sessions.