I'm having issues keeping Oblivion from crashing on my new build. I've never had this issue before on my XP based, nor my Vista based systems.
System:
OS: Windows 7 Home Premium 64bit
CPU: i7 950 @ 3.2Ghz
GPU: 580 GTX 1.5GB vRAM
RAM: 6GB DDR3 1600mhz

Game Version: Steam GOTY Edition (Incl. All Knights of the Nine/SI Expansion Packs)

Mods: (Game crashes with these both disabled and enabled)
((NOTE: This isn't my load order))
Qarl's Texture Pack 3
RAEVWD
RAEVWD: SI
Martigen's Monster Mods 3.0
Better Imperfect Water
Improved Trees and Flora
Improved Signs
Improved Fruits, Vegetables and Meats
Guard Behaviour Overhaul
Ren's Beauty Pack (Both Hairs and Mystic Elves)
Realistic Physics
Ambient Town Noises
More Immersive Sounds
Open Cities
Animated Window Lighting System 5.4.0
Oblivion Stutter Reducer
Streamline 3.1
Unofficial Oblivion Patch 3.2.0
Unofficial Shivering Isles Patch 1.4.0
Unofficial Official Mods Patch 1.5.0

Try setting permissions on your steam install folder, and all sub-folders, so UAC doesn't bite you in the rear.