Symptom:For "no obvious strange reasons" (actually for a good reason, see the cause below) the Windows 7 desktop suddenly freezes. For example, you cannot "right mouse click" on any items on the desktop. But Start Menu works just fine.
Cause:This turns out to be iexplorer.exe process not completely closing down. You can find out if this is actually your case by going to the task manager and manually killing the iexplore.exe (may have *32 next to it if you are running a Windows 7 64-bit version)
Fix:This may be due to the IE configuration or plug-ins being messed up. You can optionally reset the IE settings using this information.
IE is totally a fine browser but you can use Firefox as your default browser and you can avoid this problem in exchange for possibly other problems.
Around June or July of 2012, my Google Chrome is starting to exhibit similar behavior. I am investigating but usual "clean everything" seems to be working.