Currently Being ModeratedMay 21, 2013 1:33 PM (in response to bkb2013)
I have this very same problem. My iPhone 4 just deleted my contacts for the third time.. After the first time I made a backup on my computer, which broke down right after the second time I had no contacts (talk about great timing).
The third time I actually saw happening: phone was being charged, all of a sudden starts buzzing and shows a black screen with the 'loading' icon and the 'Slide to unlock' screen, one after another. Apart from that it did nothing anymore, so I had to reset it (home button + on/off button). After that: contacts gone. AGAIN..