Well, I have a tascam and a Roland and a motu, and throughout the night I took turns with them all. I may be wrong in this assumption, but every attempt had me connecting my hd500 via midi, not USB, and receiving a good connection, then changing cables from hd 500 to DT 50 with the midi in from interface to midi out on DT 50, midi out on interface to midi in on DT 50, each time the hd500 was recognized, the dt-50 was not. I was only explaining about the registration prompt as that is when the problems began. I attempted to update through out the night, and even when the dt 50 was not recognized, I attempted manual interface by selecting port and channel etc. I have no problem purchasing another midi interface if the three units I have some how are not adeQuate,  but as each time the hd 500 is immediately recognized , on every interface I have, I would be very dissaponted to spend money on an interface that I have no use for, if afterwards it is determined that the problem is not the interface. I appreciate the advice, and am just very frustrated as I doubt 3 midi interfaces that I regularly use with a myriad of gear will connect the hd500 but not the DT 50, although it is possible. I also see in the forum, that the only other poster with the exact same issue, same error code, using multiple interfaces, solution was to exchange the unit. Is there a hard reset for the DT 50, so that I can at least revert to previous firmware? At this point, I have never used the amp.