iTunes freezes on Sign In to iTunes Store - Windows 7 64 bit

In the last 48 hours I have not been able to use my iTunes software as it hangs immediately after launching.

I have tried a number of options to rectify the problem including Repairing the iTunes installation, Uninstalling/Reinstalling the program and System Restore to name a few. After some hours of searching I have established (after reading support.apple.com/kb/ts1717) that when I remove the Roaming Preference Files I am able to run iTunes however at this point it no longer automatically signs into the iTunes store. The problem arises as soon as I enter my user id and password the program becomes unresponsive.

I would appreciate any thoughts or suggestions anyone could provide to help rectify the problem.

Thanks