The yellow Missing Mesh warnings keep popping up above my characters head. I need to know how to troubleshoot this.

Oblivion.esmAll Natural Base.esmOscuro's_Oblivion_Overhaul.esmKvatch Rebuilt.esmBetter Cities Resources.esmUnofficial Oblivion Patch.espUOP Vampire Aging & Face Fix.espOblivion Citadel Door Fix.espDLCShiveringIsles.espUnofficial Shivering Isles Patch.espBetter Cities .espLoadingScreens.espNatural_Habitat_by_Max_Tael.espAll Natural - Real Lights.espAll Natural.espAll Natural - SI.espKvatch Rebuilt Weather Patch.espEnhanced Water v2.0 HDMI.espAmbientTownSounds.espWindowLightingSystem.espClocksOfCyrodiil.espClocksOfCyrodiil_BC_OBC_OC_OCLR_Vanilla.espLiving Economy.espLiving Economy - Items.espCutthroat Merchants.espDLCSpellTomes.espDLCSpellTomes - Unofficial Patch.espOscuro's_Oblivion_Overhaul.espOOO-Water_Weeds.espPersuasionOverhaul_OOO.espOOO-WaterFish.espCyrodiil transportation network 1.3.espKvatch Rebuilt.espLetThePeopleDrink.espDLCBattlehornCastle.espKnights.espKnights - Unofficial Patch.espP1DkeyChain.espPersuasionOverhaul.espAlternative Start by Robert Evrae.espMerchantsAlwaysBuyStolen.espRenGuardOverhaul.espBetter Cities Full.espBetter Cities - VWD of the IC.espBetter Imperial City.espBetter Imperial City FPS Patch.espBetter Cities Full FPS Patch.espBashed Patch, 0.espB79_Talos Plaza House.esp

If they're appearing above your head in third-person view then the missing mesh is probably on some piece of clothing/armor that you have equipped.

You can use http://www.tesnexus.com/downloads/file.php?id=21862 to look through your equipment and find the item one that has a missing mesh. RefScope will show you the path of the missing mesh, as well as the mod that the item belongs to, so you can figure out which mod isn't properly installed.

http://tesnexus.com/downloads/file.php?id=16704 is another popular tool for doing this sort of thing.

Note that both of these tools require http://obse.silverlock.org/.