I'd try the standard stuff like clear your cache and preferences. Other than that, it might be good to post some more information or a screenshot of what you're getting. If I get the chance, I'll try to import FCP XML and then export OMF to see if I can replicate the problem.
Gave that a shot, unfortunately didn't help. I'd send the XML, but I don't know as if it would do any good without the 400 or so media files.
I have had the same and other problems with OMF export ... I wish Adobe would get this working or provide better documentation on the problems. I also wish they would add a way to export CS5 audio tracks to their excellent application Audition 3 which I would rather use than Pro Tools anyway!
I have found that deselecting all the video tracks (no eyeballs) helps sometimes. The OMF export chokes on time remapping, nested sequences and other of PPro's cool features. I have also had problems with audio in the timeline which was inserted as "subclips" from the bin - the exporter can't find the audio file.
Hope this helps, I haven't really solved the problem either.