The semaphore timeout period has expired

I got this error message on my SharePoint farm backup (using the STSADM command
STSADM.EXE -o backup -directory \srv001sqlbackups -backupmethod full):

Object SharePoint_Config failed in event OnBackup. For more information, see the error log located in the backup directory. SqlException: Write on "\srv003SP_Backupspbr0001000001D.bak" failed: 121(The semaphore timeout period has expired.) BACKUP DATABASE is terminating abnormally.

My first thought was that it conflicted with another backup job, so I moved the start time for the backup several times to see if that helped. Obviously it lost connection to the SQL server. But to move the start time did not help. I googled it but did not find anything helpful and after having analysed the Event Viewer errors and the backup log error, I saw that the error message was displayed almost immediately after the backup had started. And then I realised that maybe it had to do with the time limit for the backup job instead of a timeout against the SQL server. So, I increased the time limit in Scheduled tasks (which runs my bat file) with a couple of hours and then the backup went through without any errors.

Just one of those error messages that are hard to determine the right solution for....