Using MS MapPoint, (& Streets and Trips,) I found that *sometimes* you have to watch what you import with regard to blank records, or possibly in your case a blank field which is being used for geocoding, ie: zipcode.

While this experience is not specific to .udl file types, you might try a test import range of data (query, view, range, table whatever) that does not have any blanks, at least in any fields that MapPoint looks at (Key, and geocoding fields like: zip, addr1, or any field that is not "Other data" etc.)

If you find that solves the issue, you might edit your tables so that blanks are filled with something else that will not cause an error with MapPoint. If the error still appears, try removing all blanks in fields you assign to "other data" in MapPoint interface as well. Especially if these fields are used for grouping Multi-Symbol Maps, or any action for which MapPoint has to look at them.

Hope this helps,
JSAS