Unable to add contact on iPad running iOS4.2.1

I was unable to add contact on my new iPad 16GB WiFi with iOS 4.2.1. When I launched contact app in background and tried to enter a new contact, after the content is in, the "Done" button didn't work.Then if I shut down of contact app or remove it from background, the problem will be solved. The iOS 4.2 contains this odd issue.