I'm a little late to the conversation, David, so I hope you've figured this out.
I work at a studio that is mostly PT based, but I use N4/5 to edit regularly. I've had plenty of problems delivering from Nuendo to PT (both OMF and AAF), and ended up spending some time to figure out what was making PT choke upon the import of both formats.
A few notes worth sharing -
PT does NOT like border of fade ins and fade outs touching one another - ie., in Nuendo, if the end of your fade in on the audio file butts right up agains the start of your fade out, PT will not import. This can be as little as one region and it will mess up the entire import;
I haven't had much luck with maintaining track names/region names when going from Nuendo to PT;
Delete Overlaps will make your life easier when going from one DAW to the next;
One workaround I've used, although it's terribly time consuming, is to export batches of selected tracks from Nuendo to PT to pinpoint what the problem is. Once you find a set of tracks that doesn't translate, export 5 min timeline chunks until you then get a set of tracks within a specific timeline range to further pinpoint where the problem lies. Although it's a PITA, I've found that it's usually only one region or audio file that's causing the problems.
I've had far less problems with N5, though I've been editing and mixing most of my projects in N5 and not transferring to PT.