Hello TC
Your problem could be caused by any number of issues. Typically Win 7 is very stable and reliable.
You say everything was working great. Until when exactly? What did you change or install at that point?
I had issues with Anti-virus programs running properly under my version (Win7 Pro 64 bit) and after inquiring in this forum about it, I installed Microsoft Security Essentials. It's a free anti-virus program, written and provided by the same people who wrote windows. And it works perfectly.
My suggestion would be to un-install all anti virus programs you currently have, and install Microsoft Security Essentials and see if that helps.
It can be found at the following link:
http://www.microsoft.com/security_essentials/
Good luck and Welcome to the Forum!