Hi Christof:
The 2nd error msg is from the OS and as far as I know can't be disabled since there is no generic File blocking msg in Windows, Storage Exec uses this msg to alert the user. I don't if you seen the error msg but you get a similar thing with Quota msgs where you would get the alarm action notification (net send) and then the OS msg not enough space is available... (sorry I don't remember the exact msg).
The product is working as designed, the error msg is a backup to when messenger service is disabled on the machine...
_Shazam