unable to delete entries

The last two days i have started building my Endnote library (endnote x5 on mac os x 10.7.4) ,
but although everything worked fine at the beginning, recently i am facing the following problem: For some reason Endnote refuses to delete any entry! No matter which way i try (drag and drop to the trash, Edit-Clear, or selecting which of the duplicate entries i will keep, the result is the same: no entry is deleted...
Is there something i am doing wrong, or something i could do to solve this problem?

Hello, vgeor:

This is usually caused by an issue within the library’s data. I recommend following the steps here to recover your library:


This will extract the data from your current library and put it in a new library. If you still experience this issue even in the new version of the library, please respond here so that we can assist further.

I hope this helps! Have a great day.