Windows 7 ultimate x64 application crashing.

Hello, I recently upgraded my computer and did a clean install of windows 7 ultate x64 and I installed all the programs I want including skype, utorrent, limewire and a few others. Everything ran fine with no lag and no signs of crashing. Then I did windows updates, reatarted my computer and it did something on the boot screen in the process of booting up then it restarted again and when I opened skype, it logs me in for half a second then it crashes. I already installed flash player, java, and all that stuff. I have the same programs on another compter and all the updates installed and it doesn't have a problem at all. Here are the specs of my computer: windows 7 ultimate x64, xfx nforce 750i SLI motherboard, inter core 2 quad q9550, 8 gb DDR2 800 MHz ram, nvidia geforce 9600gt. I also have avg Internet security suite 9.0 if that helps any. Thank you very much!