AVG Slows Down Vista?

Question

I installed AVG anti-virus and internet security and now windows vista and all the programs I run in it experience occasional "gaps" where the screen will freeze from anywhere from 20seconds to two minutes. It seems almost like there is a lag of some sort, but I don't know why. I have 2gb of ram which I know isn't the most out there but should be sufficent to run a simple anti-virus right? How do I stop the "gaps"