2001 Prius shutting down when driving problem

I need some help (and so does the Toyota dealership) in figuring out this mysterious problem that has developed in our Prius in the past two months. we will be driving along, usually on a long trip after several hours of driving, but sometimes after a shorter time, when suddenly there is a little bing sound and all the warning lights come on, the triangle, main battery, PS and exclaimation mark, and the prius starts slowing down and no longer responds to the gas peddle. So we sit for 10 to 15 minutes and restart the car and everything works fine, all the warning lights go away, etc. It has happened most often when it is hot outside and we have the air conditioning on (another problem as it cycles on an off) and are also charging a cell phone or using a plug in GPS. We took it to the dealer when all the warning lights were on and got codes of P3101, 3190, 1120 and C1521/22. The mechanic told us that they had seen other prius' with this problem when the oil level was overfilled, which was true of ours (had just had an oil change and the station had filled it to full). They suggested that we lower the oil level and get a fuel injection cleaning. I emptied out a quart and went on a 300 mile trip. Everything seemed to be going fine for 250 miles, except for the air conditioning, until it did it again - waited 10 minutes and did the return trip with no more problems. I've since added some injection cleaner and will be getting the air looked at tomorrow but wonder if anyone else has had this problem and has found a fix. The dealer said that the next thing to try is a $500 accelerator sensor. We have 159,000 miles on the Prius and replaced the small 12v battery with a new toyota one in the past 8 months. thanks in advance for any advice you can give.