Whenever I attempt to open my items menu, or open the inventory of a container or dead body, it takes about 30 seconds for it to appear. The Skills, Magic, and Map all open quickly as normal, but items takes a very long time to open up. Taking or placing an item can also take just as long. The worst of all is when I try to take or place an item into a followers inventory, this can take up to 10 minutes for the action to take effect. During this time, the screen is frozen, and I can't pull up the Xbox Guide. I have cleared my cache, and installed, uninstalled, and re installed the game.

This might not matter but I'm level 45 with about 130 hours.

i just reached lvl 45 too, and menus suddenly became very laggy/slow

any tips to fix this?

ok i found out the slow inventory menus was connected to a dwarmer museum key that had duplicated itself to close to 30000. i killed a random, planted the keys on him, waited 30+ days, saved over previous game, problem solved

I noticed that there have been other people having problems with the dwemer museum key replicating itself. Because this bug was so obscure, I thought was caused by some random corruption that had damaged an object in the game, causing it to self replicate. But the fact that this bug seems to be popping up with regularity suggests there is something wrong with that particular key.

Here is a link with someone else experiencing the same problem.
http://www.gamesas.com/topic/1332421-my-game-commited-suicide-because-off/

In my case I its ramdom ...sometimes is lighting fast and sometimes it takes forever ...im not sure what is the cause and it was like that before i had the key of the lab as well so ....nothing too much of a problem for me anyways....

is it every time you go to the menu loot? or is it every so often? do you see 'Autosaving...' in the upper left of the screen?

When its autosaving its understandable ..but mine sometimes just stays there and does not respond witht he d-pad or joystick ......again sometimes is really fast but not always i guess it depends on the amount of data the game its caching at the time....

it also may be due to how many items you are carrying on you, I have noticed a delay when I move my items from one house to another

as well as what your follower is carrying.