My wife has an iPad2 and I upgraded it from iOS 4.x to 5.1.1, using iTunes on a MacBook Air with Lion.
At the end of the last step (synchronyzing old content from iTunes copy) I get the following message (approx.): "iTunes could not synchronize Contacts because they are being used by the iPad. Close Configuration of Contacts and retry". Very strange. If I tell iTunes to synchronize, the same happens. Of course it is configured to sync all contacts. I have turned the iPad off and on and the same happens.
After that, Contacts is simply dead in the iPad, it doesn't even open. When going to Configuration and tapping on "Mail, Contacts and Calendars" item on the left list, the Configuration app silently closes. Other content (music, books, photos, Mail configuration, Safari favorites) seems to have been correctly synchronized.
Clearly something is wrong with Contacts in the iPad. I have no experience on it; were it a Mac I would know lots of things to do (erase preferences, reinstall, etc.). I think one cannot erase and reinstall the Apple apps, am I right ?
I would love to hear from similar (successful) experiences, or any idea of what to do.