Ok, I'm at a bit of a loss. It should work.
Here is an Apple support page that might help. When you are doing the various steps, be sure to read any options you are given carefully, so that you don't accidentally overwrite your iPad or iPhone's info with the less complete MobileMe account. Merge is always a save bet. At worst you'll have duplicate addresses to delete.
MobileMe: Troubleshooting iPhone, iPad, or iPod touch sync issues
If all else fails, you can try this next, but I don't guarantee results. It's just what I would try. But as a precaution I'd only work with one of the two devices until I had it working right. I'd even turn off the MobileMe contact syncing on that device until done. Be sure to Keep the contacts when you do. That way you've got a backup of your contacts if things go wrong.
Do you have a PC or a Mac? An alternative on the is to sync your Outlook on a PC, or Address Book on the Mac directly with your computer via iTunes. Then you can sync the computer with MobileMe. Unlike the iPad and iPhone you can choose to reset MobileMe's contracts when pairing it with a computer.
I'll go over the Mac stuff if you want, but I suspect you have Windows something, since MobileMe setup on the Mac is almost automatic.
To sync your iPad to the computer using iTunes, you use the Info syncing tab in iTunes when the iPad is connected. Be sure to turn it back off when done, or it can cause problems with the MobileMe sync when you start using it again. Do not use the Advanced stuff at the bottom, or you'll end up overwriting the iPad or iPhone withe the computer's data.
Here is how to set up MobileMe with Outlook after you have the contacts in Outlook.
MobileMe: Syncing your MobileMe contacts with your Outlook contact folder