See "Conditions for setting the DTC": http://www.ls2.com/boggs/a4/DTC%20P0757%205.7.htm

Basically, "Shift Solenoid B Stuck On", as detected by the ECM's algorithm.

But, if your file has P0757 set to Not Reported, then the ECM should not be setting it...

However, someone has seen similar behaviour regarding P0420 with the P10 and/or P12 ECM...

So we don't know why at the moment.