I myself tried to do some attaching while in minmus orbit and I've got a very similar problem.. Though in my case the kerbal just get's knocked a bit back, the part stays in space close to the kerbal (now with the name "<kerbal name> debris"), and my space station goes spinning and flying away.. I've tried 5 times (I only quicksaved because of the post I saw about this problem, thank god), and it happens every time, with all parts I've tried (Docking Port, Docking Port Jr., Radial Parachute). I don't have KAS installed, just KIS.. Could Kerbal Joint Reinforcement have something to do with this? Unless it happens to people not using KJR also..