Did you create a completely new account or update the existing one ? If you created a new account then any
content bought/downloaded via the old one will remain tied to that old account, and it can't be copied or transferred to a new account, so you will need to get your old account re-enabled in order to download updates to its apps.
You might be able to get it re-enabled it via this page : http://iforgot.apple.com
Or you might need to contact Apple : http://www.apple.com/support/itunes/contact/
If you've changed the password on the old account but the iPad isn't recognising it, then try logging out of your account on it by tapping on your id in Settings > Store and then log back in and see if that 'refreshes' it on the iPad.