I uninstalled AVG 2011 and installed AVG 2012 on my work computer (actually a spare work computer) and now IE will not open. It still have internet access since everything still updates. But if you try to open IE, the window will open (with nothing in it) and then close a few seconds later. WTF did I hit? I did this on both the other work computers as well as my home one and their fine
What OS are you using on each machine? There may also be a program installed that is interfering with AVG. If you are looking for a good free anti-virus, Avast free version is nice and does real time virus scanning.