I had the same problem. I was watching a football game on WatchESPN, in mid September ... It would not turn off. Hit the reset button, all I got from there on was the ACER logo. Called ACER. Warranty up 2 weeks earlier. They wanted $200, but I refused.
After much research, trial, and error, I got it working this last weekend! It is actually very simple. It is only a software problem.
1.) Download a copy of the Update.zip of the android version you want to put on it (Google A500 update.zip).
2.) Copy it to a Micro SD (leave the file named update.zip) in the main directory.
3.) Put the SD in your A500 and do a manual factory restore. (Volume+ and Power Button, then flip the rotation lock button) It will look for the update file on the SD card and put the OS back on the tablet.
I put ICS back on. After 2 days it is working perfect. I can't believe I could have done this 3 months ago.
PS. I still hate ACER Support for not helping me with this!