CPU spike = game lag?

I play Counter Strike Source and every once in a while the game will just studder, slightly, but it can still make a difference. And I was wondering if it could have to do with my performance spiking to 50 dropping to 20 than doing the same it's just up down all the time.

Could it be a virus of some sort? Even though S&D and Avast have not found anything

I had a problem where Avast would briefly take it upon itself to scan a large file on high priority, so my game would stutter. Have a go at disabling the Standard Shield (only temporarily) and play some CS. If it cures it, you'll have to find out which files (usually logs) Avast is checking, and either cut down their size or stop Avast from checking them altogether..

Of course, it could always be something else

try turning off any spyware/anti-virus software you're using. if you cannot get the studdering to stop it may be a not-enough-ram-studder, but i dont know enough about your system to make a guess like that. spiking like you're seeing is common to an anti-virus trying to check something much like the previous post says

Thanks guys I exit out of Spybot S&D at that seems to take care of it. Thanks for all the help