S1 IS problem w/ AC adapter

Ok this is pretty long winded, but its really important. Here's the low down. I have a plan to drive to Portland, OR from the SF bay area up the more "scenic" route 101, taking pictures along the way with my S1 IS to create a time lapse video. Unfortunately, I've hit a road block and I REALLY hope someone can help me with what may be the problem.

I bought a Canon AC adapter to plug into a power inverter that I will be using to power the camera and my laptop in order to keep it taking pictures consistently without changing batteries (ugh) every little while. Makes sense right?

Well I got it in, so I tested it with the camera immediately. Powered up perfectly. Seemed great. Put it away for a day while I waited for the inverter to show up. Once it did, I went out and tried it in my car...powers my laptop beautifully, but with the camera AC adapter if I try to turn the camera on to take pictures it freezes up and goes into a cycle of trying to turn on and off constantly but never staying on. The lens goes from all the way in to maybe a quarter inch out and back in, or goes all the way out and it just hangs up and freezes. When that happened once I put the batteries back in just to reset it (because the mode selection/on/off button wouldnt work) then plugged in the AC forgetting about the batteries. It tried to boot up but then it sort of just took a picture all by itself (only viewable from the view finder, not the LCD even if its out) of whatever it was pointing at, with a random part cut out laterally in a white strip, then it fades to monochrome and slowly fades completely white when that occurs.

The preview mode works fine powered by batteries, plugged into a wall, or plugged into the inverter if it makes any difference. It just hangs up hard if I try to set it to take photos.

Cliff notes-

Batteries-
Works fine, previews, takes pictures, turns on and off just fine.

AC Adapter-
Only the preview function is operational, and the on/off works if only going between preview and off.
When trying to set it to camera, it either freezes up and turns on and off constantly moving the lens in and out a little bit from fully retracted continually displaying the opening image on the LCD, or a split second of what should be displayed on the LCD (what is actually in front of the camera), but then immediately resets and repeats. The other possibility is that it would extend the full distance out, capturing a random image ahead of the lens and fades to monochrome then white...........??

I checked with my multimeter and the adapter does put out the proper voltage. Somewhat obvious since the preview part works though.

Something is terribly wrong in the circuitry related directly to the AC adapter for the camera mode, but what confuses me is that it works with preview just fine, and using batteries it can do both.

Any help would be GREATLY appreciated, I'm really running out of time to get this to work =(

Not with the adapter, I suspect, but rather with the inverter. Inverters, especially the cheaper ones, don't put out the best quality AC current; this is probably what you're seeing. Sure, it's 110V, but the wave form is probably pretty bad, not a pure sine wave like mains AC voltages show. And whenever the phase changes, basically it turns on and off the voltage. In "Preview" the power demands aren't as heavy as the demands under "Camera", so the camera can "coast" through the reversals.

Thank you for the reply, but that's actually what I thought at first too until it no longer worked plugged into a real wall socket, either. Leading me to believe something inside the camera ate may have ate itself (due to being powered once by the inverter? that doesnt make so much sense though...)

The camera still works fine, just in picture mode with the AC adapter anywhere, it doesn't. I'd like to believe the adapter died, but it still powers the camera fine for preview, but when I try to switch to picture mode it snaps a shot then does that fade thing I was mentioning...