Sorry to hear that the other steps did not help. I probably should have included a note about the factory reset in the first post.
The factory data reset will clear all data from the internal storage and will clear all apps and associated data. It will boot you to a revovery image as if you had never used the tablet. You updated to ICS, so Honeycomb is no longer on your tablet. The OS will be the same you have been running, which in this case is ICS. After the boot, you'll be presented the initial startup screen as if you just bought the device from the store.
There are two ways do this:
1.) The first and easy way is to go to Settings-->Backup & Reset-->Factory data reset
2.) There is also method to use that is intended for when you can't even boot the system, and it is described here: Acer Support: Frequently Asked Questions list for Internal Only - How do I perform a Factory Data Reset if my Acer ICONIA TAB A500 does not boot?
The second one can be tricky, but if you do it correctly, it will work. I'd use the one from Settings at this point, but I just wanted to let you know there are two options.
When you get the screen to automatically restore apps and data after the first sign in, I suggest that you uncheck that option so you can manually install apps after testing first with the builtin tablet software. I do this so I don't automatically recover problem data and apps from Google Play. There are times when you may want to use the automatic data restore service from Google, but this is probably not one of them because of the peculiar problem you are seeing.