Is the iPad on the same wireless network as the computers that do work?
When you go to the networks settings as I described before, look at the entry in the DNS field. If you know where to check it on the computers, you can compare and see if they are the same.
Another thing you can try is to manually change the DNS entry. Tap on the field and delete the current entries. Replace them with 8.8.8.8 and see if that helps.