When Nokia's Lumia 900 briefly went out of stock in AT&T stores, we weren't sure if it was because of the phone's popularity or if AT&T was waiting to give customers new versions that came with a software patch for the Lumia's data connectivity issues. Now, Nokia has told AllThingsD that its phones really are selling out that fast. "The inventory situation is primarily a function of demand," said Nokia spokeswoman Karen Lachtanski.

She also confirmed that the supply hadn't been affected by customers swapping their original phones for a patched version. "Most customers are opting to keep their units and simply update via Zune, so the impact of customer swaps is insignificant. We are producing more devices to satisfy demand as quickly as possible." Anyone who buys a Lumia 900 between now and midnight on April 21st will also get a $100 credit on their AT&T bill — a pretty good deal for installing a patch yourself. Obviously, Nokia probably wouldn't have gone on the record to say people were returning its flagship phone in droves, but it looks like the company agrees with AT&T that sales have exceeded expectations.