Yes, this is something we've seen. Some possible causes:
1) Users who are disconnected suddenly due to network or power blips. This can cause Server to think they're still attached, or sometimes can cause database corruption that causes Server to be unable to close databases gracefully.
2) Databases with large turnover - large numbers of records that are replaced with delete / import operations. This sometimes causes indexes to become corrupted, which can cause the database to hang and fail validation (which can cause the server to throw a fit).
1) Check network connections. Make sure your networks are reliable. Replace questionable hardware.
2) Check the logs for events where users are being disconnected. If you see a significant number of these, you may have issues.
3) Run a Recover on the database (use a backup and don't put the recovered copy into production). What you're looking for is the log file that's created during the process. See if there are any errors or warnings. These can indicate problems with the database structure.
This is just off the top of my head. Let us know if there are other indications.
Thank you Mike. This is really helpful. I will try your recommendations. If I find anything interesting, I will share it here so other can use it as well.