When the TC light comes on, the car does not move. A power off/on seems to reset and it goes away. I have this car for 10 days and seen it "twice" already. Did a search and did not find details to such issue.
Totally random, are you sure it's not hill start assist? Are you pressing the brake hard? Do you hear beeps after that? Not sure if the Rav4 EV has it but 2010+ Priuses have it. See http://www.youtube.com/watch?v=7aEDLzssSaU.