The HJT log file looks good . please try the batch file to repair MMC DLLs from my previous post & let us know how it works.
may not work, but its worth trying to open event viewer to check application & system logs (start>run>eventvwr.msc) , if this didn't work, then try running the command SFC /scannow
Windows XP CD will be needed for this ,you can also try installing ADMINPACK.MSI which is initially aimed at system admins, but has all the needed Snap ins. finally reinstalling SP3 can also help.
http://www.microsoft.com/downloads/details.aspx?familyid=c16ae515-c8f4-47ef-a1e4-a8dcbacff8e3
hope this helps