don't want to get snarky here, but the nextel 7100i bb doesnt officially support the 4.2 dtm and reccommends against it at every turn.....they also dont have instructions for a clean uninstall on the 4.2 software like they do on the 4.1.
unofficially i would suggest that you get every little piece from very little crevice that has anything to do with the 4.2 and then try and put on the right dtm.(4.1).
to date i have seen this done 3 times and it has failed each time. utterly unable to completely get rid of the 4.2....perhaps someone on the sprint side has a set of 'clean uninstall' instructions for the 4.2.
i assume there is a piece of dtm 4.2 that has insidiously imbedded itself into the pc.
thats just my opinion for what it is worth.