Solid Works crashes when I try to do this cut. I've done this before and I believe this must be a bug in the 2011 SP 3.0. If I do the cut upwards throught the part SW crashes when I do the flatten command. If I do the cut halfway up or not through the flange, flatten the part works. I've attached pictures and the part so who that wants to try and help me have the opportunity. Open the part and try the cutting and flattening of my part.