Hello everybody,
I spend several hours last night and finally get it back to work.
First what did not work:
I connected the iPad with iTunes an click restore. But when it asked I choose restore from last backup. Even before any app or data where restored, the contacts crashed again.
What works for me:
Disabled all apps and data from synching with iTunes
Click 'restore' in iTunes.
I the middle of this process the iPad (not iTunes) asked about the restore mode.
Choose option 'as new iPad'
Then I got a new blank installation without external apps or data. But with working contacts.
I set up my connection with exchange and other mail accounts.
Then I enabled all apps and data (photos, music, podcasts) one by one and synch.
Note: I am running a german version, so I dont know the exakt english names.
Hope that helps. Good luck.