AutoCAD 2010 :: XClipped Block Appearing Outside XClip Boundary

I have drawn a special brick pattern that I need to use at the hatch for a three story building.  The idea was to draw the pattern on a large scale and then use xclip or clipit to crop the pattern to the openings in the wall, i.e. windows, doors, etc.  The polyline that I'm using to clip the brick pattern block is quite complicated.  When I use it to clip the block, stray lines appear OUTSIDE the boundary.  The xclip frame does match the boundary I want.  Note, the entire block isn't appearing, just a row of lines here and there.  It's obviously a glitch of some sort.