i realized after reinstalling the client (thanks for fucking up the client with the last update) after the first login, or in other words, when interface/addon is first created, only 4 of the 12 blizzard_ folder are getting created. and that causes this error, depending on which folder is missing
"Your game interface files are corrupt. Please remove your InterfaceFrameXML folder"
for example, shift clicking on the battleground icon in a battleground to display the mini map, folder Blizzard_BattlefieldMinimap is missing.
or clicking on an ah npc - Blizzard_AuctionUI is missing.
folder list:
Blizzard_AuctionUI
Blizzard_BattlefieldMinimap
Blizzard_BindingUI
Blizzard_CombatText
Blizzard_CraftUI
Blizzard_GMSurveyUI
Blizzard_InspectUI
Blizzard_MacroUI
Blizzard_RaidUI
Blizzard_TalentUI
Blizzard_TradeSkillUI
Blizzard_TrainerUI
i had to ask guildies for theirs