|I get the message "Interface action failed because of an AddOn," so I turned on the taint log.
5/27 07:49:13.376 An action was blocked in combat because of taint from PocketPlot - TargetFrameToT:Show()
5/27 07:49:13.376 Interface\FrameXML\TargetFrame.lua:812 TargetofTarget_Update()
5/27 07:49:13.376 Interface\FrameXML\TargetFrame.lua:343 TargetFrame_OnUpdate()
5/27 07:49:13.376 TargetFrame:OnUpdate()
This is repeated a couple of dozen times, since I turned the log on the other day. Unfortunately, I can't duplicate the exact circumstances of getting the error. It happens when something aggros to me, or when switching targets.