Apple Inc. has halted the delivery of a small number of iPad 2s as some of the iPads carried identity codes already in use on other Apple products, which could cause problems on Verizon's network.

Numerous posts were made on Apple's support forum by owners of iPad 2s complaining that they can't connect to Verizon Wireless's CDMA 3G network.

The cause of the problem is that many of the iPads were shipped with duplicate MEIDs (A Mobile Equipment Identifier), which is a unique number that is used to identify a mobile device when it connects to the network. Two devices cannot have the same MEIDcode.

Duplicate MEID numbers were flashed onto an extremely small number of iPad 2 units for the Verizon 3G network, an Apple spokeswoman told Reuters.

Apple Stores are also reportedly compensating with $50 store credits to customers who are exchanging the non-connecting iPads with new ones.

Apple said this week that the number of iPads sold reached the 25 million unit milestone in just 14 months. The figure means about 8 million iPads shipped in the June quarter, exceeding analysts' expectations of 7 million units sold.