Are you seeing the itunes logo and usb pic on the ipad screen? If yes, then its in recovery mode.
Make sure you're using the latest version of itunes on your computer, 10.7.
Unable to update or restore
It seems form what you have said that you have tried recovery mode a few times with no success. Other than continuing to try and see if it will eventually work, I have read here on the iPad forum, that if you let the battery run down completely - and then try the process again, you may finally have success,
But if you do let the battery run down, you will have to recharge the iPad for a while before you attempt recoverymode again.