Definition of Kick Catch Interference?

Good evening MGoBloggers. I am watching the Utah BYU game right now. It is a dandy. If you have CBS College Sports Channel, I would highly recommend turning to it now. But I just saw a kick catch interference penalty against Utah, and it reminded of two incidients against Michigan that made me livid at the officials. Now, the one tonight was definitely a penalty. The Utah player pushed the BYU player before he had a chance to catch it. But there were two times this season against Michigan, one against OSU, and I believe the other was against Purdue, where the PR caught the punt, but then there was contact* by the opposing team AFTER the Michigan PR caught and secured it. I always thought that if you touch the PR after he makes a fair catch, then this was regarded as kick catch interference, but neither of the times this happened to Michigan a penalty was called. Can some one clear this up for me? *by contact, I mean that they didn't hit him, but there was more contact than I would like. I believe against Purdue, the opposing player fell on the PR, and against OSU, he was kinda pushed. P.S. My apologies if this is a repost.