I've tried OMAP flash. It looks like it completes without any errors, but the phone still doesn't respond to get into Download Mode. Nothing happens, it just remains off.
When I connect it to my computer it keeps disconnecting and reconnecting 11 times (I counted), after that it doesn't reconnect. It's like it's turning on and off 11 times and gives up after that. OMAP flash makes the connection last longer, and completing the flash resets the count back to 0, then it will go again for 11 times. Removing all sources of power to the phone also resets the count.
Anyone have any suggestions? Would a USB jig be helpful?