repeated error message about damaged library

Today, my Endnote library kept freezing up and giving me the following error message:

"This library appears to be damaged. Please verify that no other user has the library open simultaneously with write access. If this error persists after restarting EndNote, please repair the library using the “Recover Library” command on the “Tools” menu.”

The error did in fact persist after restarting Endnote, so I repaired the library as directed. Endnote froze up again during the repair process and I forcibly shut the program down. However, it seemed to have saved the file anyway, so I started working in the new file. After a few minutes, I started getting the same error message.

Any idea what is going on, and how to fix it? Thanks!

It helps to know the operating system (and build) and the version of endnote (including the updates installed, if any) .