Now I see you're using Vista.....unfortunatly Microsoft has a habit of releasing their OS's before they're properly tested......in other words they usually have a ton of bugs in them....I tend to wait at least a year or two before getting a new OS, after the release. The truth is, it could be anything, a virus, spyware, an OS fuck-up......God only knows. If it was mine, I'd try to re-install the OS again....I wish I could tell you more....