Bethesda reveals a fix for Loading problems in Oblivion.
If you're experiencing unusually long load times while playing Oblivion (including loading of menus, dialogue, sounds, objects, levels, etc.), Bethesda has posted an explanation and simple solution.
Game data that is cached on the Xbox 360 HDD can become (on rare occasions) overly fragmented, resulting in exaggerated load times. To solve the problem, just reboot the console and immediately hold down the A-button (or any button) while the game is loading — release the button once the "Bethesda Software" logo appears. Doing so will dump the old hard drive cache, fixing the problem. It's important to note that this will not affect your saved game data.