Saving as V8 when using V7.5?

[Dewglass]

V1.2 cable
V7.5.7 Build 296
LS1B PCM

Did some changes to a tune (and saved as different name) and tried to cal flash -but the truck did not start. So I tried a full flash of the previous tune and it still won't start?

Disconnected/re-connected battery. -no luck.

Is it the fact that when I saved the files it was saved in V8 the reason it won't start? (Although a .ctv extension) or is this irrelevant? Diagnostics say the PCM is ok and the connection was OK etc-even did a successful test flash?

only oddity is that my only option was saving as V8. (.ctv)

UPDATE 1:

Down loaded latest V7.5.5 (B 309) and the message is: "boot loader rejected" with test flash. (PCM status is ok.)

UPDATE 2:

re -tried cal flash the next day with success-but no start? Repeated with earlier (known good) tune- no start. It wasn't until I went back to a two year old tune the truck would start?

Seems something is screwy with the software.

It's confusing when you have a V1.2 cable and limited to V7.5.5 software but when you attempt to save ANY file it says Saving as V8 (.ctv)