Norton Internet Security automatically being disabled

On 2 occasions recently (in the past 2-3 weeks) I have powered up my laptop to get a warning message from MS that neither MS Firewall nor Norton Anitvirus software is running. I started Internet Security right away as laptop was still booting.

The first time, I was immediately hit with attempts to gain access to my machine as soon as the WiFi connected , which Norton blocked repeatedly as it went through its repair protocols and scans. To be honest, I don't recall now what it found, but I think maybe a Trojan of some kind, but I'm guessing. Today, it's still running the scans and there are no immediate attempts to gain access. I've also used my laptop many times since the first time the software was turned off.

Just wondering if anyone has the same recent experiences or ideas. I'm running Windows 7/Office 2010 on a Sony VAIO. I've had no lapses in Norton Internet Security subscription and am a pretty conscious "scam" detector due to my field of work.