FYI, in case anyone else sees this problem.
Newest version of DM780 released this week is locking up as soon as you transmit. I've tried with several different configurations (HRD, MiniDeluxe, DDUtil), both CAT and virtual PTT keting, makes no difference. Still locks up. HRD tried to say it was RF but with radio power at zero it still happens.
Many HRD users with various radios are having this issue with 6.2.8
I've reverted back to 6.2.7 for now and opened a ticket with HRD staff.
73, Dave, wo2x