I have bought a brand new computer not just because of many problems I was experiencing running Premiere Elements but in large part because of this factor. I have installed Premiere Elements with my project copied over from my old machine. I have run the 9.0.1 updater.
The computer I am using has
Intel Core i7-2600 CPU @ 3.40 GHz
64 bit Windows 7 Ultimate OS Service Pack 1
8 GB memory
When I try to move a video clip to another place in the time line I am repeatedly getting runtime errors.
Try doing the same thing in a new project. Your old project that you copied over may be corrupt.