What Marco posted is helpful.
This deals directly with the impex system, Jerry is the person that maintains that code and you'll get a faster responce from him if you post in the impex forum at vBulletin.com.
There aren't many people here familar with impex, I for one have not used it in many years and would have to spend a lot of time re-learning it to even began helping you in this situation. You need to go to the source, and the source is Jerry!