Version 4 was one of the most stable builds and caused very few problems for anybody.
Sorry your machine can't handle it. But thanks for sharing.
BTW, you do know that version 4 isn't designed to work with AVCHD video, don't you? That didnt' come until version 7. So it's a little unfair to blame the software if you're not using it properly.
Yes, when PrE 4 was being written, AVCHD was little more than a white paper and no, then released camera, recorded in that format.
As Steve points out, AVCHD support wasn't written into the program, until PrE 7, which was designed to handle it, provided that one's computer has plenty of CPU power (very, very important).