I'm running WIN7 Home Premium, 32-bit, SP1, and ran into a problem with Spybot's scheduler. Other posts suggest running Spybot as an administrator but that seems more a workaround than a fix. Here's a fix that worked for me:

Navigate to Start/All Programs/Spybot S&D folder/Spybot S&D icon. Right click the icon and select Troubleshoot Compatibility. The troubleshooter reported Spybot isn't fully WIN7 compatible and suggested running it in XP compatibility mode. After saving the new settings and exiting the troubleshooter, Spybot's scheduler performed perfectly.

Good luck!