CorelDraw X4 thinks all Illustrator files are corrupted?

Every once in a while I need to import an Illustrator file that a customer sends me. I don't recall that this was ever a problem before upgrading to X4, but every time I've tried to open or import an Illustrator file in X4 it tells me that the Illustrator file is corrupted. I doubt if these files are actually corrupted, since I don't recall ever having problems before X4 and it seems very unlikely that suddenly every Illustrator file I get from different sources is corrupted. I conclude that the problem is most likely with Corel. Any suggestions?