I also had this same problem on my iPad 2, but then I decided to remove the other MobileMe account that I had converted to iCloud. This was a separate account from my main MobileMe account, which was the first account that I converted to iCloud. I was able to add the secondary account, and the iPad 2 told me that it could not be used as a primary iCloud account (because I already had one setup) but could still be used for Mail, Contacts, and Calendars. I only wanted to use it with Mail, so that's how I setup it up. But, I noticed that it also showed Documents and Data in the Mail, Contacts, and Calendars settings, under Accounts. However, when I clicked on the account for more detail, Documents and Data was not listed. So, at the time, I didn't think much of it. But, then when I started using Numbers and Pages and noticed the problems syncing, I decided to remove the secondary account and re-add it. Once I removed it, the documents immediately appeared in Numbers and Pages. I then added the seconard account back, and it successfully added (this time only reflecting Mail as the service used). So, I thought I'd share. I'm chalking this all up to some kinks in a fairly new system. I expect things will get better as Apple works through them.