Unable to add particle effect...in Tower

Attempting to clear Tower map, entered boss room and took Brutus to half health. Shaper appeared, said his little thing in the freeze frame, and then got an error:

"Unable to add particle effect to bone group named Larmfx. From AO:Metadata/Monsters/CityStalkers/Female/AtlasofWorldsBoss.ao. From EPK:Metadata/Effects/Spells/monsters_effects/act4/Shavronne/Brutus_tormented_lightning_aura_epk.epk"

OKing the dialog box exited the game.

Rebooted game, found to my relief that I did not die and portals were still up. Reentered portal to Tower from my hideout and went through Tower to the boss room. Was immediately presented with identical dialog box, pressed OK, game forcequit again.