Last time I checked these plugins install 2 files ( extensions.rb and sketchup.rb) in the Plugins folder which do not belong there. (They go all the way back to SketchUp 5.)
These files should already exist in the Tools folder, and if you really want to use these "power" toolbars, you should delete extensions.rb and sketchup.rb from the Plugins folder (but not the Tools folder) unless you are actually using SketchUp 5.