And so there was. The common.diag log-file was a wropping 13,5 GB and was filling the entire drive! The file contained a lot of mumbo-jumbo lines.
The quick fix was to move the file to another drive, and restart the server. Now was the time to find the cause of the issue. After restarting the server the issue was still there since it didn’t take long for the file to reach 300 MB.
Searching the Sametime forum on developerWorks I found what looks like a solution to the problem. The issue is apparently only present for Sametime 6.5.1 on Windows 2003 Server with SP1 and there is a quick-fix until a proper fix is developed. The fix is described in technote 1203311 at IBM.com.
I’ll apply the fix (editing the registry) tonight and see what happens.