Numerous reports are coming in from various forums showing users getting multiple error messages when trying to buy the new Halo 2 maps on an Xbox 360. Many users see "Purchase failed. You will not be charged for this transaction. Please try again later." This is happening even with a credit card associated with the Gold account. Another error users are seeing is "Installation of content failed".
There's also many reports of big glitches in the new maps, such as multiple invisible walls in Tombstone.