I make use of the gear renderer all the time and haven't run into this before, I don't think.  I am running 0.47, downloaded just today from inkscape.org, on mac OS X Leopoard. When I render a gear, I cannot get the boolean operations to work with it.  So if I want to make a "hole" in the center of the gear, I can't put a circle there and do a difference operation to cut a circle into the center of the gear. From a 2D standpoint, this would not be a big deal, but since I import the gear .svg files into Blender for later 3D operations, this is something of a problem.  What am I doing wrong, or what is it about the gear paths that is preventing this?