Unable to run Windows Update

My system has stopped allowing the Windows Update function. Sys. level is W2K-SP3. When I select Windows Update I get to the part where it allows me to scan for updates. This is the
http://v4.windowsupdate.microsoft.com/en/default.asp page.
After it has completed the scan I click on Critical Updates and Service Packs and it ultimately times out with an "unable to display page ". The only thing I can think of as occuring concurrent with the Update stoppage is that I have started to run a frequent regimen of Spy-Bot, Ad-Aware, Reg Cleaner, System Mechanic and BHOdemon.
I admit that my system is lean and mean, but I fear that it has become exposed to security problems. Appreciate any advice as to fix of bypass.