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Periodically the software updates require a restart. It's best to do it before trying anything else. If it is constantly asking you to restart even after you've already done that then there is possible corruption so the best thing you can do is as follows.
Uninstall via Control Panel/Add or Remove Programs (XP), Programs/Uninstall a Program (Vista/Windows 7)
Use the MCPR removal tool linked under Useful Links above and reboot.
Reinstall from your online account.