Did you see that article that sample utility is compiled from? (
http://www.mp2kmag.com/importersub01.asp ) I'd recommend go to that and debugging from there.. When I compiled that utility for the newsletter I remember running into some shapes the code would not handle without some tweaking and presumably you've found more cases..
You might try starting over with a clean map -- it could be there's an errant line or point somewhere that's it's tripping up on.
Eric