I had this same problem and i was missing a .txt file that needed to go along with the game apparently.
It can be found under Documents>ElderScrollsOnline>Live
There should be a .txt that is called UserSettings.txt
One option
Locate the line "SET RequestedNumThreads "X" change the X from whatever number it may be to 0.
Otherwise sorry for the long post. Credit goes to ZOS_RobertM
If the UserSettings.txt file is not present in the My Documents/The Elder Scrolls Online folder, here's what you'll need to do (apologies in advance for the immense amount of text):
Open a new text document in Notepad
Paste the following information into the text document
SET MouseRawInput "1"
SET MouseSensitivityFirstPerson "0.50000000"
SET MouseSensitivityThirdPerson "1.28999996"
SET MouseSmoothing "0"
SET InvertMouseWheel "1"
SET InvertMouseY "1"
SET InvertMouseX "1"
SET CachedRLREnabled "1"
SET CachedReflectionResolution "4"
SET CachedShadowFiltering "5"
SET ScreenshotFormat "BMP"
SET PregameGammaCheckEnabled "0"
SET HardwareCheckEnabled.2 "0"
SET SUB_SAMPLING "2"
SET REFLECTION_QUALITY_v3 "2"
SET PARTICLE_DENSITY "3"
SET HIGH_RESOLUTION_SHADOWS "1"
SET SHADOWS "4"
SET GAMMA_ADJUSTMENT "112"
SET VIEW_DISTANCE "1.69000006"
SET GPUSmoothingFrames "10"
SET MIP_LOAD_SKIP_LEVELS "0"
SET RAIN_WETNESS "1"
SET LENS_FLARE "1"
SET GOD_RAYS_v2 "1"
SET ANTI_ALIASING_v2 "1"
SET AMBIENT_OCCLUSION "1"
SET COLOR_GRADING_v1 "0"
SET BLOOM "1"
SET DEPTH_OF_FIELD "1"
SET COLOR_CORRECTION "1"
SET SOFT_ALPHA "1"
SET DISTORTION "1"
SET CHARACTER_LIGHTING "1"
SET DIFFUSE_2_MAPS "1"
SET DETAIL_MAPS "1"
SET NORMAL_MAPS "1"
SET SPECULAR_MAPS "1"
SET CLUTTER_2D "1"
SET SIMPLE_SHADERS "0"
SET WATER_FOAM "1"
SET VSYNC "0"
SET MAX_ANISOTROPY "3"
SET FULLSCREEN_v5 "2"
SET PreferMaximizedWindow "0"
SET FullscreenHeight "0"
SET FullscreenWidth "0"
SET WindowedHeight "768"
SET WindowedWidth "1024"
SET SOUND_ENABLED "1"
SET FOOTSTEPS_VOLUME "50.00000000"
SET FOOTSTEPS_ENABLED "1"
SET SPEAKER_SETUP "0"
SET BACKGROUND_AUDIO "0"
SET VO_VOLUME "70.00000000"
SET VO_ENABLED "1"
SET UI_VOLUME "70.00000000"
SET UI_ENABLED "1"
SET AMBIENT_VOLUME "70.00000000"
SET AMBIENT_ENABLED "1"
SET SFX_VOLUME "70.00000000"
SET SFX_ENABLED "1"
SET MUSIC_VOLUME "70.00000000"
SET MUSIC_ENABLED "1"
SET AUDIO_VOLUME "59.00000000"
SET AUDIO_ENABLED "1"
SET TooltipFilter "2"
SET TooltipNumOptions "2"
SET EffectsLookupViaBinarySearch "1"
SET Language.2 "en"
SET GraphicsDriver.7 "D3D11"
SET PatchDataPath "HYPERLINK "https://portal.obj.cs.zos/f5-w-687474703a2f2f67616d65$$/GameData/"game:/GameData/"
SET CacheDataPath "HYPERLINK "https://portal.obj.cs.zos/f5-w-687474703a2f2f6d616368696e65$$/Cache/"machine:/Cache/"
SET GameCameraFirstPerson "0"
SET AcceptedEULAVersion "2"
SET DirectionalDamageIndictorVisibleInThirdPerson "0"
SET CameraFramingTransitionEnabled "1"
SET SkipPregameVideos "0"
SET HasPlayedPregameVideo "1"
SET RangedKillCamera "0"
SET PlayerKillCamera "1"
SET LastMonsterKillCamera "1"
SET MinFrameTime.2 "0.01000000"
SET ParticlesEnabled "1"
SET RequestedNumThreads "0"
SET FreeUnusedGrannyFileSections.2 "0"
SET IsTrustedMachine "1"
SET RememberAccountName "1"
SET AccountName ""
SET LastRealm "NA Megaserver"
SET CustomUIScale "1.00000000"
SET UseCustomUIScale.2 "0"
SET RollDodgeDoubleTapEnabled "1"
SET RollDodgeDoubleTapTimeWindow.2 "185"
SET CameraZoomDistancesSynced "1"
SET SiegeCameraZoomDistance "6.00000000"
SET WeaponsOutCameraZoomDistance "2.00000000"
SET WeaponsSheathedCameraZoomDistance "2.00000000"
SET MaxNetworkWriteBuffer "10485760"
SET MaxNetworkReadBuffer "10485760"
Save the file as UserSettings.txt in the My Documents/The Elder Scrolls Online folder
Restart the launcher
I had this same problem and i was missing a .txt file that needed to go along with the game apparently.
It can be found under Documents>ElderScrollsOnline>Live
There should be a .txt that is called UserSettings.txt
One option
Locate the line "SET RequestedNumThreads "X" change the X from whatever number it may be to 0.
Otherwise sorry for the long post. Credit goes to ZOS_RobertM
If the UserSettings.txt file is not present in the My Documents/The Elder Scrolls Online folder, here's what you'll need to do (apologies in advance for the immense amount of text):
Open a new text document in Notepad
Paste the following information into the text document
SET MouseRawInput "1"
SET MouseSensitivityFirstPerson "0.50000000"
SET MouseSensitivityThirdPerson "1.28999996"
SET MouseSmoothing "0"
SET InvertMouseWheel "1"
SET InvertMouseY "1"
SET InvertMouseX "1"
SET CachedRLREnabled "1"
SET CachedReflectionResolution "4"
SET CachedShadowFiltering "5"
SET ScreenshotFormat "BMP"
SET PregameGammaCheckEnabled "0"
SET HardwareCheckEnabled.2 "0"
SET SUB_SAMPLING "2"
SET REFLECTION_QUALITY_v3 "2"
SET PARTICLE_DENSITY "3"
SET HIGH_RESOLUTION_SHADOWS "1"
SET SHADOWS "4"
SET GAMMA_ADJUSTMENT "112"
SET VIEW_DISTANCE "1.69000006"
SET GPUSmoothingFrames "10"
SET MIP_LOAD_SKIP_LEVELS "0"
SET RAIN_WETNESS "1"
SET LENS_FLARE "1"
SET GOD_RAYS_v2 "1"
SET ANTI_ALIASING_v2 "1"
SET AMBIENT_OCCLUSION "1"
SET COLOR_GRADING_v1 "0"
SET BLOOM "1"
SET DEPTH_OF_FIELD "1"
SET COLOR_CORRECTION "1"
SET SOFT_ALPHA "1"
SET DISTORTION "1"
SET CHARACTER_LIGHTING "1"
SET DIFFUSE_2_MAPS "1"
SET DETAIL_MAPS "1"
SET NORMAL_MAPS "1"
SET SPECULAR_MAPS "1"
SET CLUTTER_2D "1"
SET SIMPLE_SHADERS "0"
SET WATER_FOAM "1"
SET VSYNC "0"
SET MAX_ANISOTROPY "3"
SET FULLSCREEN_v5 "2"
SET PreferMaximizedWindow "0"
SET FullscreenHeight "0"
SET FullscreenWidth "0"
SET WindowedHeight "768"
SET WindowedWidth "1024"
SET SOUND_ENABLED "1"
SET FOOTSTEPS_VOLUME "50.00000000"
SET FOOTSTEPS_ENABLED "1"
SET SPEAKER_SETUP "0"
SET BACKGROUND_AUDIO "0"
SET VO_VOLUME "70.00000000"
SET VO_ENABLED "1"
SET UI_VOLUME "70.00000000"
SET UI_ENABLED "1"
SET AMBIENT_VOLUME "70.00000000"
SET AMBIENT_ENABLED "1"
SET SFX_VOLUME "70.00000000"
SET SFX_ENABLED "1"
SET MUSIC_VOLUME "70.00000000"
SET MUSIC_ENABLED "1"
SET AUDIO_VOLUME "59.00000000"
SET AUDIO_ENABLED "1"
SET TooltipFilter "2"
SET TooltipNumOptions "2"
SET EffectsLookupViaBinarySearch "1"
SET Language.2 "en"
SET GraphicsDriver.7 "D3D11"
SET PatchDataPath "HYPERLINK "https://portal.obj.cs.zos/f5-w-687474703a2f2f67616d65$$/GameData/"game:/GameData/"
SET CacheDataPath "HYPERLINK "https://portal.obj.cs.zos/f5-w-687474703a2f2f6d616368696e65$$/Cache/"machine:/Cache/"
SET GameCameraFirstPerson "0"
SET AcceptedEULAVersion "2"
SET DirectionalDamageIndictorVisibleInThirdPerson "0"
SET CameraFramingTransitionEnabled "1"
SET SkipPregameVideos "0"
SET HasPlayedPregameVideo "1"
SET RangedKillCamera "0"
SET PlayerKillCamera "1"
SET LastMonsterKillCamera "1"
SET MinFrameTime.2 "0.01000000"
SET ParticlesEnabled "1"
SET RequestedNumThreads "0"
SET FreeUnusedGrannyFileSections.2 "0"
SET IsTrustedMachine "1"
SET RememberAccountName "1"
SET AccountName ""
SET LastRealm "NA Megaserver"
SET CustomUIScale "1.00000000"
SET UseCustomUIScale.2 "0"
SET RollDodgeDoubleTapEnabled "1"
SET RollDodgeDoubleTapTimeWindow.2 "185"
SET CameraZoomDistancesSynced "1"
SET SiegeCameraZoomDistance "6.00000000"
SET WeaponsOutCameraZoomDistance "2.00000000"
SET WeaponsSheathedCameraZoomDistance "2.00000000"
SET MaxNetworkWriteBuffer "10485760"
SET MaxNetworkReadBuffer "10485760"
Save the file as UserSettings.txt in the My Documents/The Elder Scrolls Online folder
Restart the launcher