Oblivion uses the Xbox 360 hard drive extensively to cache (copy and reuse) game data. This is done to optimize all loading the game does. It has been found in rare cases on some Xbox 360s that the cached data can get overly fragmented. This exhibits itself by the game taking a long time to load anything from menus, dialogue, sounds, objects, levels, and more.

To solve this problem, reset your Xbox, and hold down the A button as the game is booting up. If any button is held while Oblivion is loading, it will clear its hard drive cache, and create a new one

I'm afraid that incorrect. They're available for two days already in Singapore.

http://bob.com.sg/forum/showthread.php?t=23240