Thank you all, I have solve the problems... The way to put out text inside a note is really a good clue to find mistakes because in this way I dont need to delete nothing...
The first problem, exactly as you told me, it was because the image was inside a format called parragraph, despite of I deleted the text before where I though it was the problem, the format continued there... The next problem was due to special characters introduced at JabRef and that lyx couldn't support... The special character it was the name of an author, that I have change to solve it... The name it was Babuška, with this strange "s". I hope he didnt mind so much to be called Babuska ;P Thank you very much, I felt unable to continue for a while.
