I have a feeling that it's caused by the AWLS mod together with Open Cities Reborn, but so far I haven't found any word of a conflict in either of their descriptions. Does anybody know whether there's a patch available, or whether this could be caused by something else?

Here's a couple pictures:

http://img.photobucket.com/albums/v510/mattkaine/Oblivion/Oblivion2010-08-1216-39-46-08.jpg
http://img.photobucket.com/albums/v510/mattkaine/Oblivion/Oblivion2010-08-1216-40-23-96.jpg

And here's my load order (yes, I do organize it with BOSS):

Oblivion.esmAll Natural Base.esmFrancesco's Leveled Creatures-Items Mod.esmFrancesco's Optional New Items Add-On.esmFrancesco's Optional New Creatures Add-On.esmTamrielTravellers.esmOpen Cities Resources.esmTNR ALL RACES FINAL.espTNR - ShiveringIsles.espYounger Hotter NPC's v1.0.espUnofficial Oblivion Patch.espUOP Vampire Aging & Face Fix.espOblivion Citadel Door Fix.espDLCShiveringIsles.espUnofficial Shivering Isles Patch.espAll Natural - Real Lights.espAll Natural.espAll Natural - SI.espEnhanced Water v2.0 HD.espCities Alive At Night.espWindowLightingSystem.espAliveWaters.espAliveWaters - Koi Addon.espAliveWaters - Slaughterfish Addon.espAFK_PrayerIdles.espP1DrobesOver.espP1DlookHereYou.espCrowded Cities_Open.espCrowded Roads Revisited.espEVE_StockEquipmentReplacer.espextavegant masks.espSlof's Horses Base.espFrancesco's Optional Files.espTamrielTravellers.espShiveringIsleTravellers.espFransfemale.espExtended Imperial City Version 1.0.espExtended Chorrol Open Cities.espExtended Skingrad Open Cities Complete.espBrumaMGRestored.espKnights.espEVE_KnightsoftheNine.espxulStendarrValley.espXulEntiusGorge.espxulFallenleafEverglade.espxulColovianHighlands_EV.espxulChorrolHinterland.espxulBeachesOfCyrodiilLostCoast.espxulBravilBarrowfields.espxulLushWoodlands.espxulAncientYews.espxulAncientRedwoods.espxulCloudtopMountains.espxulArriusCreek.espxulPatch_AY_AC.espxulRollingHills_EV.espxulPantherRiver.espxulRiverEthe.espxulBrenaRiverRavine.espxulImperialIsle.espxulBlackwoodForest.espxulCheydinhalFalls.espxulAspenWood.espxulSkingradOutskirts.espxulSnowdale.espOpen Cities Outer Districts.espOpen Cities Reborn - Full Merge.espOCC-ULCH-Patch.espOCLR+ULBWForest Patch.espOC+Cheydinhal Falls Patch.espOC+ULSkingradOutskirts Patch.espHarvest [Flora].espEVE_ShiveringIslesEasterEggs.espDungeon Actors Have Torches 1.6 DT.espExterior Actors Have Torches 1.3 DT.espEnhanced Vegetation [125%].espRealisticForceMedium.espRealisticMagicForceMedium.espMighty Magick - Settings.espMighty Magick - Spells and Creatures.espMighty Magick - Shivering Isles.espMighty Magick - Races.espBetter Redguard v2.espFrancesco's 10 days respawn time - 1-20 day lenght rescale.espP1DshieldNoGlow.espomg-dynamicDoF.espOpen Cities Reborn Road Record.espBashed Patch, 0.espMK_Mask.espThe Undead Arise 2.0.esp

Thanks for any help I may receive.

Now I have no idea at all. Upon deactivating AWLS via OBMM, the meshes of Leyawiin's building disappear and leave missing mesh objects in the places where the building were on the river. Could it have something to do with the Unique Landscape mods I use?

Go to tesnexus and down load Refscope. Use it It will tell you all of the information about an object such as what mods use it and or referance it.

Turns out it was because of Cities Alive at Night. Thanks for the tip!