Hello
Obviously, something is corrupt in Windows causing the Task Scheduler to malfunctioning. Have you checked the CBS.log to find out which files are corrupt? For how to read CBS log, please take a look at the below Microsoft KB article.
How to use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7
http://support.microsoft.com/kb/929833
I also suggest you run In-place Upgrade with a Windows Server 2008 DVD to fix this problem permanently. In-place upgrade will scan and repair the corrupt files while it won’t impact your programs and documents data.
How to Perform an In-Place Upgrade on Windows Vista, Windows 7, Windows Server 2008 & Windows Server 2008 R2
http://support.microsoft.com/kb/2255099
Thanks
Zhang