Help: My car loses electric power while driving & then dies

Hi, I don't know a whole lot about cars, but I love listening to Car Talk and I've posted questions here before and have been very impressed with your responses (Thank you!). I was hoping one of you could help me with a new, rather urgent problem:

I have a 2001 Nissan Maxima SE Automatic with approx. 106,000 miles. I drove down to Virginia Beach (from New York city) on TuesdaY for the holiday weekend. Towards the end of the drive (9 hours) I was sitting in traffic and my ABS, Emergency Brake and Battery lights flashed on the dashboard. The car was making a funny noise under the hood (it was a brief hydraulic kind of noise), which after reading the manual, I suspect was the ABS diagnostic system. The manual said it was normal for this test to happen periodically, at slow speeds when I first start the car. In thise case however, the dashboard lights would come on, then disappear and then come back on intermittently. I got off the highway and out of traffic and the lights went away.

After that, everything was fine until about 5 PM on Christmas day (Thursday). I had done some local driving and I was sitting at a stop light when the hydraulic noise came back and my dashboard lights came on again. After a few blocks, all my gauges went dead and the car just lost power. I was in drive when it happened and I couldn't get it started afterwards; it wouldn't crank. A good samaritan helped me push it into a nearby gas station. I was worried initially about leaving it there overnight, because I had the driver's side window down and I couldn't get it to go back up. After sitting with it for about 20 minutes, I put the ignition into auxillary mode and was able to get the window to go back up (weird); I did not try starting it.

I left it there overnight and the next morning (Friday) I called a tow truck to take it to the nearest Nissan Dealer. While waiting for the tow truck, I turned the key and it started right up! No dashboard lights flashing or any other signs of problems. When the truck came, the guy looked under the hood and said there was a lot of corrosion on my battery and this could cause the problem. I mentioned that I lost power while driving and he said it was probably the alternator.

I drove it to the Nissan dealer, about 15 minutes away, and when I pulled into the parking lot, it died again; same deal as before (airbag, ABS, break & battery lights came on and then the gauges died). The dealer ran some tests and told me my battery was dead and the corrosion was so bad that the wires that connect the battery to the car were being held together by the corrosion. They replaced my battery and the connectors and then cleaned everything up. I asked about the alternator and they said they tested it and it was fine.

I drove away and the car was fine until late Saturday night. As I was driving, the airbag light came on again and this time the dashboard light and clock went really dark; this is the first time it died at night. This kept up for awhile and then it felt like the brakes were being pressed every few seconds while I was driving (I was on the highway and not touching the brakes). This kept up for a couple of minutes and then the car lost power again (all gauges went dead and my headlights went out). I coasted off the highway and pulled onto the shoulder of the nearest exit ramp.

I called for a tow truck and had my car towed back to the Nissan dealer. Since today is Sunday and they're not open, I have to wait until Monday to have them re-examine my car. I was hoping to get some more information before then and figure out what's going on. I'd like to be able to ask them to check other things, besides just the battery, the connectors and the alternator... what else could be causing the problem?

My biggest concern is that I have to drive back to New York on Monday and I am concerned about breaking down again.

Please help.