I use Adavnced Windows Care & CCleaner to fix problems like this. If you have uninstalled something it may have ripped out the required DLL file with it.
You can trya and download the NET framework patch from Microsoft if you want. Both the above programs are free downloads. With CCleaner be wary of cleaning out all your cookies as it will do a good job of getting rid of all your automatic sign on links to your favourite websites!