Does this happen with all PDFs, or only with one/a few? It would also be useful to have some minimum information about your setup, such as OS, and versions of OS and Reader.
If you are using Windows, you could try to do a system restore.
Go to the restore date/point that is nearest to the time before you uninstalled and re-installed your Reader after it malfunctioned
I've had that happen to me before and that's all I did.
Hope that helps.