The following knowledge base article says you can unlock with another computer, but you will loose the information on the iPad when you do so.
Otherwise, the only option is the computer you last used to sync.
Xtremely silly feature as I just found out. Someone in the office has just locked my Ipad on purpose, and now has rendered it useless until I get home and sync the Itunes at home so I don't lose the data... I was really surprised with this "feature" Imagine if you were away overseas/ on assignment...
I'd prefer the thief to get locked out every 30min...
Hope this is changed in the future...