OS - Windows 10 64 bit; CPU - Third-gen i7; GPU - ATI HD 7xxx; RAM - 24 gigs
Broken: Blender hash 211b539
Short description of error
You get bad results when adding a subsurf modifier and following it up with planar decimation on a mesh with holes (faces start overlapping the holes and each other).
Exact steps for others to reproduce the error
Open the .blend file and turn the decimate modifier on and off