First bug: The whole Kvatch quest has been translated into French.
Second bug: The doors to the Sigil Stone room in the Kvatch Oblivion tower thingy have been removed.

I haven't a clue what could have caused these bugs or how to sort them out, but I'm guessing it's a mod. Load order?

Posting your load order would be good.......

Load Order.

Oblivion.esmunderdark.esmCobl Main.esmMart's Monster Mod.esmDremoraCompanion.esmFort_Cooper.esmCM Partners.esmToaster Says Share v3.esmTRoN.espDLCShiveringIsles.espNatural_Weather_by_Max_Tael.espNatural_Habitat_by_Max_Tael.espNatural_Water_by_Max_Tael.espCarcernus Prison.espM.O.E. - Undermined Leveled Gameplay - Creature Edition.espM.O.E. - Undermined Leveled Gameplay - Item Edition.espRAEVWD Cities.espRAEVWD Imperial City.espReznod_Mannequin.espMaleBodyReplacerV4.espM.O.E. - New Staffs, Blight and Ashstorms.espM.O.E. - Playable Scythe.espM.O.E. - Unlocked Palace Guard Armour.espM.O.E. - Unlocked Dremora Armour and Robes.espM.O.E. - Unlocked Glenroy and Captain Renault Blades Armour.espRTFemaleReplacerV12.espSoT_Rise of Sheogorath.espMage Equipment.espkikaiAS-SheogorathRT-sep.espAncientTowers.espCobl Glue.espCobl Si.espCobl Tweaks.espMart's Monster Mod.espMart's Monster Mod - Shivering Isles.espMart's Monster Mod - Additional Enemy NPC Vars.espMart's Monster Mod - Diverse Imperial Armor.espMart's Monster Mod - Looting NPCs & Creatures.espMart's Monster Mod - Zombies for Body Meshes.espMart's Monster Mod - Durability & Damage.espMart's Monster Mod - Spawn Rates - Increased.espMart's Monster Mod - Dungeons of MMM.espMart's Monster Mod - More Wilderness Life.espMart's Monster Mod - Extra Wounding.espMart's Monster Mod - Diverse WaterLife.espMart's Monster Mod - Diverse Runeskulls Loot.espMMM-Cobl.espCastle_Highrock.espDwemer_Skyship_1_1_0.espFort_Cooper.espM.O.E. - Tools of Kagrenac - The Secret of White Gold Tower.espM.O.E. - The Black Sacrament - Night Mother's Ritual.espSoT_TheOrderofNibenay.espKnights.espM.O.E. - Visit Valen Dreth Topic.espMart's Monster Mod - Knights.espLost Paladins of the Divines.espMart's Monster Mod - City Defences.esproad+bridges.espxulBeachesOfCyrodiilLostCoast.espxulImperialIsle.espNRB4+UL-II Patch.espNatural_Vegetation_by_Max_Tael.espM.O.E. - Bone Names and Priced Skull.espM.O.E. - Travel Services.espM.O.E. - Lucien Lachance Rumors Fix.espM.O.E. - Icons for Mythic Dawn Armour - Fix.espM.O.E. - Lycanthropy and Lichcraft.espM.O.E. - Realistic Prices, Realistic Weights, No Quest Items.espSalmo the Baker, Cobl.espBorderless_Cyrodiil-3578.espM.O.E. - Vampire Clan Raelu.espM.O.E. - Ethereal State Spell.espM.O.E. - Levitation Magic.espM.O.E. - Lock Spells.espM.O.E. - Mythic Dawn Powers.espM.O.E. - Teleportation Magic and Icarian Flight.espMadgod Powers.espTeachSpell.espSupremeMagicka.espSM_EnchantStaff.espSM_VanillaSpells.espSM_UnlockSpells.espSM_Scrolls.espSM_SigilStone.espbgMagicEV_Conjuration_for_Supreme_Magicka.espJpm's Miniature Necromancy.espRenGuardOverhaul.espactors_in_charge.espActorsInMadness.espM.O.E. - Unlocked Hairstyles.espM.O.E. - Playable Dremora and Custom Race Fix.espCM Partners.espAsharasCMPartners.espDremoraCompanion.espCobl Races.espbgBalancingEVCore.espbgMagicEV.espbgMagicItemSigil.espbgMagicEVStartspells.espbgBalancingEVOptionalFangs.espbgBalancingEVOptionalMoreEyes.espbgBalancingEVLAMEAddition.espbgBalancingEVLAMEGlue.espbgIntegrationEV.espCobl Races - Balanced.espbgMagicShaderLifeDetect.espbgMagicLightningbolt.espReal Lava 1.3.espNRB4 Standard Road Record.espBashed Patch, 0.espCharGenAmulet.esplumi_enchantments.espValenwood.espwalklikesheo.espAsharasCMBeasts.espUnderdarkMap.espTower_Of_Hadarath.espWtower.espCompanionMaster.espDock.espSummersetLandscapes.espSummerset.espVampire.espBlackscar Citadel.espSpells.espNecromancy.espCastle_Wolfspike.espRiseofMadness.espDaedra.espRoSAddon.espCultofOrder.esp00cyrstalcragfortress.espWayshrines.espXilselem.espSide's Sailing Ships.espDremora Race.espCastle.espCMCompanions.esp

It sound like you installed the french version of one of these mods. Did you run that load order through BOSS? It looks a little disorganized. Also, make sure to grab one of the Natural Weather fixes, and I recommend trading Natural Vegetation for http://www.tesnexus.com/downloads/file.php?id=23783 I do not use Natural Weather, so I cannot tell you which unofficial fix is the recommended one, but here is a link to one that seems well recommended: http://www.tesnexus.com/downloads/file.php?id=14918. You could also, instead, grab http://www.tesnexus.com/downloads/file.php?id=18305 and use the Natural Weather option. It is a wonderful mod and still supported. Plus, it incorporates four of the most popular weather mods. (You do not have to use a version that mixes all four of course.

Ok, thanks. I've found the mod that did it. It changed a lot of other cells as well. Thanks!

I figured as much, haha, glad everything is working. On another note, COBL races and RBP completely stomp on each other. Choose one or the other. I recommend RBP, since COBL races is kind of a stripped down version of it. Since you have half the modules installed for RBP anyway, I recommend kicking that particular COBL plugin.