I'd guess the AC compressor siezed up - that would cause it to stall when the engine is loaded with a 'dead' accessory.
The green light should be completely seperate - though my 07 automatic system could easily be wired different from your 05 manual version.
With the engine off, you can reach the AC compressor and move it by hand (think you need a wrench on it though), if it doesn't move that'll be your problem. You can also look at that pulley when the engine is running and someone turns on the AC, if it turns or not will be the test.
Dave - 2007 3GT - black, badges removed, door bumpers removed, auto up windows, backup sensors, adjustable HID headlight modification, current limited high beams, fog lamps able to be on with parking lights only, under seat subwoofer. I'm usually on mazda3club.com instead of here - where many of the above 'mods' are that show in my signature.
Used to have GSL-SE's too