NIS-Intrustion Prevention Switching off

For the past month I have noticed that NIS goes from "SECURE" status to "AT RISK" and every time it is the Intrusion Prevention being switched off.  I can go in and turn it back on and within 30 seconds it switches off again.

I have run both the full scan and the NPE (Norton Power Eraser) programs...there are no detected viruses.  Anybody have experienced this?  I am running Windows 7 Professional /64-bit.