It won't let me attach the screenshots, so I'll type them out.
The Login In screen error is:
Interface\GlueXML\AccountLogin.lua:21: attempt to call method `SetBackdropBorderColor' (a nil value)
And then I log into my character, the UI is all screwed up with missing textures and says
Interface\FrameXML\GameTooltip.lua:95: attempt to index global `_G' (a nil value)
Now I can't even log back on. Please assist.