This sounds like a known issue that the tech folks at filemaker have been unable to reproduce. TSGal may well respond with a request for log files and such as a result.
A simple "fix" that works in many situations is to simply close and re-open the Admin Console. In other cases, I've had to stop and start the database. This last option can be done after close of business for the day so as not to interfere with users using the database.
Restarting admin console doesn't solve this problem. I'll try to restart the server. (but with v9, that didn't solve problem...)
Which log can I provide ? I check on all but nothing appear like error, ...
If you have any schedules running (backups, scripts, ...) check their state. On my server, I found that a scheduled backup had started and then never completed. I had to force the FMS service to stop (via the windows services control panel) before I could restart and get things going again.
As to logs, I never found anything in them on mine either, but TSGal asked for them anyway.