We all know that Grand Theft Auto IV will be huge, but is Take-Two underestimating the number of acquired pre-orders? They may be in the UK, as major online retailers are starting to tell consumers something scary: they're running out of copies to pre-sell.

According to MCVUK, Play.com has already sold through its allocation of GTAIV pre-orders, and both GAME and Gamestation's online sites are issuing warnings to those who wish to pre-order the game. They're definitely running low - and we don't know how much longer supplies will last - but the good news is that stores will have more to sell on the launch day; April 29. Play.com's Gian Luzio told MCV that GTAIV is definitely a big "hardware driver," especially for the PlayStation 3.

"Sales have gone crazy and have proven to be a real hardware driver already," said Luzio. "We've sold out now, but will be getting in more stock as soon as it becomes available. We expect to have some stock back in for the day of release on April 29th."

As for the other sites, GAME's warning reads- "We cannot guarantee delivery on the day of release for orders placed on or after the 7th of April." Gamestation says something similar, and confirms they are no longer accepting pre-orders for the blockbuster title. Now, we in the US are wondering if online sites and brick-and-mortar stores will start having the same problem...if so, we'd strongly suggest pre-ordering GTAIV ASAP.