Sorry guys if this post is irrelevant somewhat but feel good that at least your DTM works. My home PC would fail to detect my BB despite having manual detection in connection manager. At work, I have no problems. I'v econducted a clean uninstall (via RIM's instructions of reg key removal and such) and reinstalled with no success. My PC detects a device connection via USB but DTM fails to be 'connected'...again despite having connection manager detecting a unit in the USB port.
It happens randomly but I guess it's worth the trouble to turn off the radio when using app loader. I haven;t had this problem with basic synching yet.