And it's not just the summon ghost spell that does it. About all starting conjuration spells fall victim to this, perhaps even all conjuration spells in general. Removing SM fixes the issue, but I don't want to play without it.
Here's my current load order:
Spoiler
Active Mod Files:00 Oblivion.esm01 All Natural Base.esm [Version 1.0]02 Francesco's Leveled Creatures-Items Mod.esm [Version 4.5bSI]03 Francesco's Optional New Items Add-On.esm [Version 4.5bSI]04 Francesco's Optional New Creatures Add-On.esm [Version 4.5bSI]05 Cobl Main.esm [Version 1.72]06 Better Cities Resources.esm [Version 4.7.1]07 HorseCombatMaster.esm08 DLCShiveringIsles.esp09 Better Cities .esp0A Atmospheric Loading Screens - Random Quotes.esp0B All Natural.esp [Version 1.0]0C All Natural - SI.esp [Version 1.0]0D Immersive Interiors.esp [Version 0.7]0E Immersive Interiors - Lights Addon.esp [Version 0.7]0F Enhanced Water v2.0 HD.esp++ Enhanced Water v2.0 HD - SI Addon.esp [Version 0.1]10 PowerAttack Voicemod.esp11 DarNifiedUI Config Addon.esp++ Item interchange - Extraction.esp [Version 0.76]12 Enhanced Economy.esp [Version 4.3.1]13 FF_Real_Thirst.esp14 Enhanced Hotkeys.esp [Version 1.2]15 FastEquipping.esp16 Hemingweys NPC Capes.esp [Version 1.02]17 XSPipeMod.esp [Version 1.2]18 Francesco's Optional New Adventurers.esp19 Cobl Glue.esp [Version 1.72]1A Cobl Si.esp [Version 1.63]1B FF_Real_Thirst, Cobl.esp++ Cobl Tweaks.esp [Version 1.44]1C TIE.esp [Version 1.37]1D TIE+Frans NPC Inventory.esp [Version 1.0]1E xuldarkforest.esp [Version 1.0.5]1F xulStendarrValley.esp [Version 1.2.2]20 xulTheHeath.esp21 XulEntiusGorge.esp22 xulFallenleafEverglade.esp [Version 1.3.1]23 xulColovianHighlands_EV.esp [Version 1.2.1]24 xulChorrolHinterland.esp [Version 1.2.2]25 xulBeachesOfCyrodiilLostCoast.esp [Version 1.6.4]26 xulBravilBarrowfields.esp [Version 1.3.2]27 xulLushWoodlands.esp [Version 1.3]28 xulAncientYews.esp [Version 1.4.3]29 xulAncientRedwoods.esp [Version 1.6]2A xulCloudtopMountains.esp [Version 1.0.3]2B xulArriusCreek.esp [Version 1.1.3]2C xulPatch_AY_AC.esp [Version 1.1]2D xulRollingHills_EV_withoutWheat.esp [Version 1.3.2]2E xulPantherRiver.esp2F xulRiverEthe.esp [Version 1.0.2]30 xulBrenaRiverRavine.esp [Version 1.0.2]31 xulImperialIsle.esp [Version 1.6.5]32 xulBlackwoodForest.esp [Version 1.0.4]33 xulCheydinhalFalls.esp [Version 1.0.1]34 xulAspenWood.esp [Version 1.0.2]35 xulSkingradOutskirts.esp36 xulSnowdale.esp [Version 1.0]37 HUD Status Bars.esp [Version 0.9]38 Quest Award Leveller.esp [Version 2.0.1]39 Alternative Start by Robert Evrae.esp3A RealisticForceMedium.esp3B RealisticMagicForceMedium.esp3C SupremeMagicka.esp [Version 0.90]3D SM_ShiveringIsles.esp [Version 0.86]++ SM_COBL.esp [Version 0.86]3E SM_EnchantStaff.esp [Version 0.80]++ SM_UnlockSpells.esp [Version 0.70]3F Enhanced Grabbing.esp [Version 0.5]40 Deadly Reflex 5 - Timed Block with no damage or durability changes.esp41 DeadlyReflex 5 - Combat Moves.esp++ SM_DeadlyReflex.esp [Version 0.86]42 Oblivion XP.esp [Version 4.1.5]++ Item interchange - Placement.esp [Version 0.76]43 bgBalancingEVCore.esp [Version 10.0EV-L]44 bgMagicEV.esp [Version 1.7EV]++ bgMagicEVStartspells.esp [Version 1.68EV]++ bgMagicEVAddEnVar.esp [Version 1.68EV]45 bgMagicEVPaperChase.esp [Version 1.68EV]46 Better Cities Full.esp [Version 4.7.0]47 Better Cities - Unique Landscape Barrowfields.esp [Version 4.7.0]48 Better Cities - Unique Landscape Chorrol Hinterland.esp [Version 4.7.0]49 Better Cities - Unique Landscape Cheydinhal Falls.esp [Version 4.7.0]4A Better Cities - Unique Landscape Skingrad Outskirts.esp [Version 4.7.0]++ Better Cities - TIE Restricted Area.esp4B Better Imperial City.esp [Version 4.7.0]4C Better Cities - COBL.esp [Version 2.1]** bgMagicEVShader.esp [Version 1.7EV]++ bgMagicShaderLifeDetect.esp [Version 1.68]4D bgMagicLightningbolt.esp** Enhanced Economy - Soulgems.esp [Version 4.2.2]4E Hemingweys Capes.esp [Version 2.00]4F Scathe.esp [Version 0.1]50 Real Hunger, Cobl.esp [Version 1.6.1]++ Cobl Filter Late MERGE ONLY.esp [Version 1.53]** All Natural - Indoor Weather Filter For Mods.esp [Version 1.0]51 Bashed Patch, 0.esp52 Streamline 3.1.esp53 All Natural - SI Settlements NIW Support.esp54 All Natural - Bravil Mages Fix.esp
If you need any more info, just ask.
Thanks in advance for your help.