Hi, what build of SEP12.1 are you running?
Its worth checking 2 things to start of with:
1. Check on your Home Screen, do the SEPM defs match the latest Symantec Defs?
If not, it's possible that your SEPM has a corrupt update. I usually download the .jdb and manually update the SEPM. It then works 100%. Check the below link:
http://www.symantec.com/business/support/index?page=content&id=TECH102607
2. In the SEPM under the ADMiN tab, force an update and see if it shows any errors.
A screenshot would help though...
Cheers