Sounds like that darn theft deterrent system is still giving you problems. I had a similar experience in my car as well. I disconnected the theft deterrent computer completely, cut and grounded one of the wires on the TDC harness as shown in this post:
http://www.toyota-supra.info/forums/...rm-system.html
Hard as hell to get at, but no problems since then.
I hope this is helpful
EDIT: I followed the instructions in burton51m's post