3 Lights and You're Out

My car is a 2007 Prius with 137K mileage. The hybrid battery was replaced in May. Today I was driving and the car went into neutral, then three lights came on: the master warning light, the malfunction indicator lamp (check engine), and the hybrid system warning light. I turned on the hazards and tried to put the car into drive. No go. Then, I turned the car off and on. The car went into drive, and I pulled it around a corner to get out of traffic. I turned it off and on again. Still the lights remained; however, I was able to take it to my mechanic. He did a test for codes, and these came up as being current on the HV ECU and Cruise Control:
P0A1D - Hydrid Powertrain Control Module
U0100 - Lost Communication with ECM/PCM A
U0111 - Lost Communication With Battery Energy Control Module "A"
P3000 - Battery Control System
U0129 - Lost Communication With Brake System Control Module

History code that came up for the engine, the HV battery, and the antilock breaks is:

U0293 - Lost Communication With Hybrid Vehicle Control System

Once the 12V battery had been tested when the car was on but not in drive, there were no battery issues. When the car was on and ready to drive, tested again, and there were no issues. Once the battery was tested the second time, all the lights went off. I test drove it, and the car seemed fine. Mechanic suggested replacing the 12V battery. Thinks there may have been corrosion that was knocked off during the testing. From what I can see, the batteries don't corrode because they are covered.

Suggestions here? I don't believe the 12V battery has ever been replaced.