When the iPad is in recovery mode and you attempt to restore, does the restore file iTunes is downloading ever complete? Does it actually try to initialize the restore? Typically iTunes will take some time to download the necessary files to perform the restore and iOS devices will only stay in Recovery Mode for so long before they restart. So that's not terribly unusual.
Now if the download is completing and it won't actually start to restore the iPad that's another story. It could be that it's not getting the start restore command from the computer. Which could be due to a number of reasons. Usual steps for troubleshooting this include swapping out the USB cables, or the port in use.