Hi Sofia,
I’m sorry to hear about your problem! It turned out that my Endnote files were corrupted. But the good news is that the technical support at Thomson Reuter is excellent - i sent them my data files and they debugged them and sent them back to me and it all works fine now.
They also said that the problem may have been caused by my back up system - apaprently Endnote is incompatible with many back up software, so now I have set mine to not back up Endnote automatically (and I do it manually). I also close Endnote before running the back up.
So I suggest contacting technical support directly and i’m sure they will be able to help you. Good luck!
Jenny