It freezes whenever you open Internet Explorer to go into the Internet, right?
Used to have this problem myself. Found out that there were malicious resident spyware programs waiting for the Internet connection to transfer unknown payload into or out of my PC. Problem was solved using a third-party spyware removal tool Ad-aware.
Your computer may be infected with spyware. Maybe Microsoft Windows Anti-Spyware (Beta) program could help:
http://www.microsoft.com/athome/security/spyware/software/default.mspx