Typically this means that you are not getting data in through port 7891
See http://www.symantec.com/docs/TECH169868
If you are in a proxy environment, and have not updated to SPC 2.1 MP1 (2.1.1.3012) please do so, as this corrects some issues with Proxy environments.
After installing this update make sure to have your proxy configured in the Admin section of the web console.
Refer to this document for the order of install for updates:
http://www.symantec.com/docs/TECH176838
Regards