I'm relatively new to modding, so hopefully this is just something stupid and easy to fix.

Here's what's happening:

I've been installing mods all night, periodically loading Oblivion to make sure everything works. It goes fine. After I get everything installed I want (for now, anyway) I go to load Oblivion up and finally play and it crashes almost immediately. There's a black screen for a second or two and then CTD. Oh my, this isn't good.

I clear all the mods and verify the game loads with just oblivion.esm and it does. I start enabling other mods one by one. Eventually, after much experimenting, I determine Kvatch Rebuilt is causing the crash. However, Kvatch Rebuilt loaded okay earlier. It must be conflicting with something. More experimenting shows that the crash happens when I have Kvatch Rebuilt and OOO enabled at the same time. I enable only Kvatch Rebuilt and OOO, wondering if maybe a 3rd mod is somehow interfering with those two. No, it still crashes in the same way.

After searching the board, it doesn't seem like anyone else is having this problem and, also, these two mods should work together with no problems. Except they don't for me. They're both the newest versions, I downloaded them within the last 24 hours. I have run my load order through BOSS as well.

I don't see how my load order would help in this case, but I'll post it anyway since that seems to be a common request if it isn't included. This load order causes a crash and is also after being run through BOSS:

Oblivion.esm
Kvatch Rebuilt.esm
Unofficial Oblivion Patch.esp
Oblivion Citadel Door Fix.esp
DLCShiveringIsles.esp
Unofficial Shivering Isles Patch.esp
Arthur_Natural_Weather_HDR_by_Max_Tael.esp
Natural_Habitat_by_Max_Tael.esp
RTFemaleReplacerV12.esp
Oscuro's_Oblivion_Overhaul.esp
Insanity's Pet Shop.esp
Kvatch Rebuilt.esp
Kvatch Rebuilt - OOO Compatibility.esp
DLCBattlehornCastle.esp
bartholm.esp
Natural_Vegetation_by_Max_Tael.esp
Kobu's Skip Intro Mod.esp
No psychic guards v1.2.esp
Kobu's Character Advancement System.esp
Kobu's Personality Enhancer.esp
Kobu's Health Modifier Mod.esp
Kobu's 2x Slower Jack-of-All-Trades Mod.esp
Kobu's Lighter Backpack Mod.esp
_Ren_BeautyPack_full.esp
MorrowfiedOblivion.esp

In addition to those, I have multiple graphics/sound enhancers installed as well. Those are: Qarl's 3, Real Wood Signs, Oblivion Stereo Sound Overhaul, New Nebular Planet, Low Poly Grass, IFT, Female Body Replacer, Enhanced Water, Dark UI'd DarN, Better Night Sky, Beautiful Stars. I don't see how these would make a difference, but I figured I should mention them anyway, just in case.

Any ideas on why I'm having problems?

Not really. Many use OOO and Kvatch Rebuilt together. I notice that you don't have an Oscuro's_Oblivion_Overhaul.esm, which means you're using an old version of the mod - or forgot to use the esm, which would lead to crash on startup. I'd suggest updating to http://www.gamesas.com/index.php?/topic/1089759-relz-oscuros-oblivion-overhaul-133/ at least, preferably 1.34 Beta 5.

Also, run http://www.gamesas.com/index.php?/topic/1096264-boss-better-oblivion-sorting-software/ on your load order and check the log - it gives notes on version numbers, issues etc.

One thing you might try is deleting the Oblivion.ini in My Documents/My Games/Oblivion, letting the game generate a new one on startup.

I used the manual install version of OOO, so maybe I screwed something up when I was copying files over. Or maybe I clicked on the wrong link and downloaded an old version. I'll reinstall OOO and see if that fixes anything. Thanks!

Just a follow up to anyone who might read this, doing a total reinstall of OOO (via OMOD this time instead of manually) completely fixed the problem. I'm guessing I screwed something up when I did a manual install of it.

So, problem solved!

Just for future reference, a crash on load just about always means a missing master. You can easily tell which mod is missing a master by looking in Wrye Bash for the red highlighted mod.