If you've backed up your apps to iTunes and have NOT synced your apps with iTunes since the update, you should be able to delete the "bad" version off the iPad and put the one from iTunes on it.
You'll not be able to update it, either on the iPad or iTunes (and both will continue to prompt you to update), but at least you'll have the old version.
If you don't have an older copy on iTunes, cause you've already synched it over ... then no, there's no way to get an old app back.
Oh, maybe you can check your Trash on your PC? Maybe iTunes puts the older versions there? <-- That's a wild guess, cause I don't really know how apps are updated (whether its the whole thing or just pieces), nor do I really know what iTunes does...
Hope some of that helps.
Marilyn