i got something similar issue like this person.
i read a post that might be the way that the 3d program export the .OBJ.
in modo UV maps are OK, but as i import them in to Mudbox as OBJ some of the vertices try to weld together, so they fly from across the UV making a mess.
http://area.autodesk.com/index.php/forums/viewthread/19402/
any one know what i might be doing wrong?