I had that happen to me and I think it was because I had
it set to automatically search for updates when opened
and I opened it when not connected to the net and it
froze on me and then would not work again , I tried
System restore but it still didnt work I tried
uninstalling then reinstalling no good in the end I had
to use a ghost backup I had from before spybot and then I
installed spybot and set it to manual check for updates ,
It has worked great since ?