I receive an error when leveling up now. I have not had a problem with this in the past. I am a level 35 mage and I can level up, but when I do, oblivion crashes to desktop. I am unsure as to what the problem is, but I suspect one of the mods I have installed is to blame. I will try this, and then edit my post with the results.

EDIT: Indeed, that was the problem. I will go through the mods and figure out which one is causing the problem. I will provide that information here, for anyone else who has this problem.

RESOLUTION: Problem found. The mod named "Combat Behavior 2.1b" is to blame. Perhaps because of conflicts.

I have this exact same problem, but I dont have that mod running. However, you reckon that it is a mod that makes it do this?
It only seems to have started happening since I got Shivering Isles. It seems most people have a short lag when levelling up, but not many people seem to have it crash when clicking the "exit" button. Maybe I'll see if it is any of my many mods that is making it crash...Unless anyone knows whats actually wrong with it?
Thanks