The March 20th BB Logging software V7.5.4 (build 44) MUST not be used to reflash LMM trucks. It will leave the controller in dead-poll and will require GM's TIS/SPS to recover the controller.
We are working on it and will release an update as soon as it is fixed.
http://forum.efilive.com/showthread.php?t=7610
Update: The March 26 beta update software fixes the problem with flashing LMM trucks. If you have updated to the March 26 release, please disregard this warning.
Regards
Paul