Norton Internet Security 2008

I’m currently using Norton Internet Security 2008 with Windows XP Home edition. My computer frequently restarts  saying that Windows has just recovered from a critical error caused by my anitvirus software. Are there any known issues that could be causing this? I don’t even have to be using my computer for this to happen and it’s happening multiple times a day. Is there anything wrong with my NIS or XP? A virus or trojan? I’d like to get this solved so this can stop happening.