'99 Silverado - flashing problems

[Boost]

I had problems today flashing a truck. It's a '99 Chevy pickup with the square headlights and "T" motor (5.3, cable driven). It read just fine, and I licensed it. It started acting up during licensing, I had the key off, so after it was attemting to boot or something 10 times on the screen, I cut the key on ( I notice that some vehicles are ok with the key off, since it's off anyway normally during licensing, but some don't like it). It gave the usual error messages in red (like data transfer interrupted, etc..) I had this happen before and it still worked. But this time after licensing it and attemting to flash, it said "bootloader rejected". Then the PCM stopped communicating, and the truck wouldn't start (actually it would fire up and die, like a theft problem). I had to reprogram the PCM with a Tech 2 to get it to run.

What is possibly causing this? I have the very latest of everything, and of course I will try again soon. Thanks!

[Lennart]

Did you unplug the V2 (OBD and USB) as well as restart the software? When mine is acting up this usually helps.

[Boost]

I'll try that also, thanks.

[Jakes4321]

This happen to me with a 2000 silvy with a 6.0. I had to use a bitch harness to tune the truck. When ever I tried trough obd2 it would do the same thing every time.
I never did get a answer for what happened but after using the harness it worked fine.

[GMPX]

It's kinda odd to have reflash problems on the older vehicles like that. Boost given your experience in the Diesel tuning (and how cranky LB7 & LLY's can be to flash), I have to ask the obvious, was there any aftermarket radio equip?
The no restart is very odd indeed, I can't see how the theft could have got messed up.

Cheers,
Ross