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All my contacts and groups are listed twice.

Do you have your contacts saved on your laptop?

I think the best thing to do would be to delete them all, using iTunes, then resync from Address Book.

Or, you could sync from your iPhone to your computer, and delete them quicker like that, then delete all from the iPhone and resync.
 
Anybody experiencing this and know how to fix it?
i had it too
are you using mobile me to push?
if so, turn off contact syncing, and say delete from my iphone when it asks
it'll delete the dupes but not turn off syncing

the only problem is, when sending a text and typing a name to send to, the name still appears twice
 
That's popped up for me a couple of time. I just deleted my MobileMe account and then added it again.

Surprisingly, Exchange has been fine.
 
Yeah I am using Mobile Me. I will try your suggestions. Thanks guys!
 
This happened to me when I simply upgraded to 3.0 rather than doing a restore. After restoring and setting up as a new phone, it was back to normal.
 
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