Windows Vista Sidebar problems

[Chris from OK]

For no apparent reason, Sidebar will not load or function. The error message
I get when trying to start any downloaded Gadget is

"Unable to load "C:\Program files\Windows\Sidebar\Gadgets\Clock.Gadget".
(identical for every other gadget besides clock.gadget)

How can I repair Sidebar? Do I re-install Vista (a scary proposition) or is
there some kind of repair tool?

Thanks in advance for your help.

 

[Bob]

Run System Restore to a time before the problem began.