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. Once you see the "Bethesda Softworks" logo video, the game is already loaded, and the cache should have been cleared.

Note, this does not effect your game in any way other than loading. You will not lose any saved data.

Q. I cannot access my downloaded plugins in Oblivion for Xbox 360 unless I am connected to Xbox Live.

Update: See This Please as the Process has been made easier

http://www.xbox.com/en-US/support/systemuse/xbox360/licensemigration/

A. The inability to access your Oblivion Plugin content on Xbox 360 unless you are connected to Xbox Live is related to the way the license usage and restrictions are handled by Microsoft. Please refer to this article for additional information and workarounds.

http://support.microsoft.com/kb/911198/en-us

When you download content from Xbox Live Marketplace, that content is licensed to the console you downloaded it on and the profile you downloaded it with. The console license allows anyone to use that content on THAT console, online or off. The profile license allows you to use the content on any console, as long as you're signed in to Xbox Live (the reason you have to be signed in to Xbox Live is that your profile has to be validated with the service).

For example, if you try to play your new Xbox Live Arcade game offline on a different console, you may find that it only plays in demo mode. This is because the console is not the console to which the game is licensed, and your profile can't be validated until you sign in. To play the full version on this other console, you have to sign in to Xbox Live.

For Oblivion gamers, this means that if you took your Xbox hard drive to a friends house to download the content using your own Xbox Live gamertag, the plugins may be licensed to your gamertag, but they are also tied to that specific console. As soon as you take the hard drive back to your console, if you are not connected and logged into Xbox Live with your gamertag, the content will not work. The same issue may occur if you have to replace or repair your xbox.

So, what that means is, if you have an Xbox 360 that is NOT connected to the internet, and you wish to play Oblivion with the Plugins, you can do so, but will need to take your ENTIRE Xbox 360 to an internet connection, log into Xbox Live with YOUR gamertag, and download the plugins. Then you can play the game and use the plugins on THAT Xbox 360 without being connected to Xbox Live.

If you had your console repaired or exchanged after you had downloaded the plugins, you would need to contact Microsoft Xbox support at 1-800-4MY-XBOX to determine ways to transfer the license to your new console.

I'm trying to I've installed the title update for Oblivion Game of the Year Edition to access Knights of the Nine and Shivering Isles., but it's not being recognized. What can I do?
There is an incompatibility with a certain version of the Dashboard (2.0.7371). Updating to the latest Dashboard version (currently 2.0.8507) will correct this issue and make the extra content load properly. To obtain the latest Dashboard update, connect your console to Xbox Live and download and install it.

If you are unable to connect to Xbox Live, you can also obtain the latest update by putting in a newly released title (anything released since August 2009), as each title would come with the latest available Dashboard version. Simply loading the game disc will prompt to install the Dashboard update.

If you don't have a newer game, borrow one from a friend, or you can take your console to a friend who has a Live connection and connect your console to obtain the Dashboard update.