Ive had a bunch of P10s fail to flash, always been able to recover them. Its always aftermarket electronics trying to communicate on the databus and messing everything up. Ive spent 45 min before with a trouble P10 with aftermarket stereo and alarm, rebooted my laptop at least twice and re-opened the tune file a bunch.

Also, another option is to try and flash using V8 (I havent tried it, my P10 truck is back at home in Seattle) or BBF it. We have 3 ways to flash the P10s now, if V7.5 doesnt work convert it into a *.ctd file and flash using another option. Food for thought.