I am running windows 7 ultimate (x32) and whenever I unlock it the taskbar and/or desktop freeze and take up a large amount of processing power. The only way to fix this is to restart explorer.exe or repeatedly click on the taskbar till the restart task option shows up. It doesnt happen every time, but it happens quite often. Are there any patches or settings that can make this stop?
I would double check that there are no pending updates just in case.
However, this sort of issue is usually down to third party software/drivers.
I would perform a general check on your machine and remove old programs you don't use that integrate in to Windows.
You may want to take a look at Microsoft / Sysinternals Autoruns and check under the explorer tab (amongst others), and uncheck items that you think could be wrong. You can then remove using the uninstaller (try first) or press delete in Autoruns.
Windows is very stable by default and this sort of activity is normally always down to third party programs and/or drivers that are coded badly.
This seems to have been an issue related to the theme I was using (The nature theme). While the suggestion was quite good, it seems there is something with the win7 themes that change desktops periodically that causes exploer.exe to freeze up when the machine is unlocked.