Remenants of mods?
Mine would crash on start up, right at the loading screen, after removing certain mods.
have you deleted the .ini flie loacated here? Documents / My Games / Oblivion
Delete the Oblivion.ini & the Render info file.
Restart Oblivion, and you will need to reset all your graphics settings.
Then try and see if it will start.
If you start up with no problems, then start adding your mods.
(Use OBMM too
It might also be worth checking the load order, and in your DATA folder deleting any the Folders:
Textures / Meshes if they exist.
A re-install may be in order too.