CCleaner will not run after a Shutdown

When I set up a Vista Task schedule to auto run ccleaner all is great until I switch off my computer. When i switch it back on the ccleaner task does not run. So I have to reinstall cleaner and start again. Whatsup?

You should not need to reinstall, however Vista+task scheduler+CCleaner = Fail as Cleaner needs elevated privilages to run (UAC Prompt must be clicked)