PreJim: you should take a look at this thread and check whether your problem is the same QHUSB-DLOAD mode problem.
Dead Pre 3 (QHUSB-DLOAD mode)
As I understood (after lots of searches and trial-and-errors) this state is unrepairable. You mostly have a brick with lots of spare parts. ((

My previous Pre 3 too entered this mode suddenly in June. Luckily I had a backup phone but I lost some of my data anyway.