I was having the error:

AssertFile: C:\_Skyrim\Code\TESV\TES Shared\misc\BGSLocalizedString.cpp

I found that to fix it I needed to add Dawnguard.bsa to the SkyrimEditor.ini

Find the [Archive] section and add Dawnguard.bsa as I have demonstrated below.

SArchiveList=Skyrim - Textures.bsa, Skyrim - Meshes.bsa, Skyrim - Animations.bsa, Skyrim - Voices.bsa, Skyrim - Interface.bsa, Skyrim - Misc.bsa, Skyrim - Sounds.bsa, Skyrim - Voicesixtra.bsa, Skyrim - Shaders.bsa, Update.bsa, Dawnguard.bsa

and here,

SResourceArchiveList=Skyrim - Textures.bsa, Skyrim - Meshes.bsa, Skyrim - Animations.bsa, Skyrim - Voices.bsa, Skyrim - Interface.bsa, Skyrim - Misc.bsa, Skyrim - Sounds.bsa, Skyrim - Voicesixtra.bsa, Update.bsa, Dawnguard.bsa

Hopefully that works for you.
I have also read that it is necessary to add sLanguage=YOURLANGUAGEHERE to the [GENERAL] SECTION. I did this too, adding ENGLISH, but it did not do anything to correct my problem. I did read reports that it worked for other people using non-English languages.

Hope this helps some people out.

Best,
-Nyram

Helps a bunch! Thanks!

Good Info, It worked like a champ!
Thanks alot!

Attempted another suggestion to extract the bsa file earlier and went from 10 errors to aprox 200 errors! That did stop the tools from crashing however, BUT!

Still getting the following errors. I can live with these, yet would be nice to see a fix/workaround.

MASTERFILE: ===========================================================
QUESTS: Could not find previous info (02015C84) for TopicInfo (02015C85) in Topic "" (02004DAA).
QUESTS: Could not find previous info (02004DE6) for TopicInfo (02018B1D) in Topic "" (02004DAA).
QUESTS: Could not find previous info (02013709) for TopicInfo (02013721) in Topic "DLC1VQ03VampireShared" (020098B2).
QUESTS: Could not find previous info (0201329B) for TopicInfo (02013709) in Topic "DLC1VQ03VampireShared" (020098B2).
MASTERFILE: Armor 'DLC01ReaperBracers' (0201A755) used invalid Biped Object slot 33 for race 'SkeletonRace'.
MASTERFILE: Unique ActorBase 'DLC01SoulCairnReaper' (0201A73E) has more than one reference in the world. Data access when unloaded may not work correctly.
MASTERFILE: Unable to find Package Target Reference (00000000) on owner object "DLC1VQ02SeranaPullLever".
MASTERFILE: NavmeshInfo 00028e37 has no parent space, ignoring
MASTERFILE: Automatic door 'ShipTrapdoor01MinUseHidden' (00099315) [0 units] in cell 'Wilderness' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'ShipTrapdoor01MinUseHidden' (00061435)
Ref: '' (00099315)
Cell: 'Wilderness' (0000967A) (2, -6) in world 'Tamriel' (0000003C)
See Warnings file for more information.
MASTERFILE: Automatic door 'AutoLoadDoor01' (00015E1D) [324 units] in cell 'YngolBarrowExterior' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'AutoLoadDoor01' (00031897)
Ref: '' (00015E1D)
Cell: 'YngolBarrowExterior' (0000B452) (38, 11) in world 'Tamriel' (0000003C)
See Warnings file for more information.
MASTERFILE: Automatic door 'AutoLoadDoor01' (0001779F) [125 units] in cell 'KarthwastenExterior03' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'AutoLoadDoor01' (00031897)
Ref: '' (0001779F)
Cell: 'KarthwastenExterior03' (0000707A) (-34, 9) in world 'Tamriel' (0000003C)
See Warnings file for more information.
MASTERFILE: Automatic door 'WRShackDoorMinUse01' (0006767F) [48 units] in cell 'WhiterunExterior10' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'WRShackDoorMinUse01' (000FE471)
Ref: '' (0006767F)
Cell: 'WhiterunExterior10' (000095DA) (7, -1) in world 'Tamriel' (0000003C)
See Warnings file for more information.
MASTERFILE: Unable to find attach ref 02006718. Attach ref data will be removed.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'sc_towerfloatingrocks03' (02010BAE)
Ref: '' (02015DCA)
Cell: 'DLC01SoulCairnCraterKeeper' (02002C75) (6, 3) in world 'DLC01SoulCairn' (02001408)
See Warnings file for more information.
MASTERFILE: Unable to find attach ref 02006718. Attach ref data will be removed.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'FXSmokeWispsLg2x1Adjust' (0001643B)
Ref: '' (02015DC8)
Cell: 'DLC01SoulCairnCraterKeeper' (02002C75) (6, 3) in world 'DLC01SoulCairn' (02001408)
See Warnings file for more information.
MASTERFILE: Unable to find attach ref 02006718. Attach ref data will be removed.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'sc_towerfloatingrocks02' (02010BAD)
Ref: '' (02015DC3)
Cell: 'DLC01SoulCairnCraterKeeper' (02002C75) (6, 3) in world 'DLC01SoulCairn' (02001408)
See Warnings file for more information.
MASTERFILE: Automatic door 'dunda14PortalDoor01' (0003DC3F) [287 units] in cell 'DA14Interior' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'dunda14PortalDoor01' (0003DC41)
Ref: '' (0003DC3F)
Cell: 'DA14Interior' (0003D62B)
See Warnings file for more information.
MASTERFILE: Automatic door 'AutoLoadDoor01' (00015D12) [307 units] in cell 'WolfskullCave01' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'AutoLoadDoor01' (00031897)
Ref: '' (00015D12)
Cell: 'WolfskullCave01' (000151F6)
See Warnings file for more information.
MASTERFILE: Automatic door 'HelgenKeep01btoExteriorREF' (000909D2) [275 units] in cell 'HelgenKeep01' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'ImpDoorSingleLoad01' (0004203A)
Ref: 'HelgenKeep01btoExteriorREF' (000909D2)
Cell: 'HelgenKeep01' (0005DE24)
See Warnings file for more information.
MASTERFILE: Automatic door 'HelgenKeeptoExterior01REF' (0005DF95) [304 units] in cell 'HelgenKeep01' has its teleport marker too close to the linked door.
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'ImpDoorDoubleLoad01' (000439C4)
Ref: 'HelgenKeeptoExterior01REF' (0005DF95)
Cell: 'HelgenKeep01' (0005DE24)
See Warnings file for more information.
MASTERFILE: Occlusion box has < 16.0 half-extent and should be switched to a plane : REFR Form '' (02014641) to STAT form 'PlaneMarker' (00000017) in Cell 'DLC1DawnguardHQ01' (02001DBA)
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'PlaneMarker' (00000017)
Ref: '' (02014641)
Cell: 'DLC1DawnguardHQ01' (02001DBA)
See Warnings file for more information.
MASTERFILE: Occlusion box has < 16.0 half-extent and should be switched to a plane : REFR Form '' (02014642) to STAT form 'PlaneMarker' (00000017) in Cell 'DLC1DawnguardHQ01' (02001DBA)
MASTERFILE: Errors were encountered during InitItem for reference:
Base: 'PlaneMarker' (00000017)
Ref: '' (02014642)
Cell: 'DLC1DawnguardHQ01' (02001DBA)
See Warnings file for more information.
MASTERFILE: Cell contains more than one COC marker:
'testFalmer' (0200362A)
MASTERFILE: Cell contains more than one COC marker:
'testGiant' (02007D95)