Date: 10/21/2008 7:14 pm EDT
Hmmm. It can take a few tiles to get the "hang of it" when snapping together. It sounds like you've already tried the dishsoap trick. The other tip would be to try to "dance" the tiles together by starting on one side, and then "swinging" the other side into place. You'll definitely want to use a tapping block and mallet.
What is the room temperature? As the temperature decreases, the tray edges tend to "stiffen" - however, as long as it is normal room temp, you should be OK.
Regarding the tiles moving, that is normal for the first row or two. I typically stand on the "in-place" tile while tapping the new tile in place. That usually will keep the original tile stationary. Generally, you may need to readjust the floor a bit as you go with the tapping block and mallet.
I'm sorry it isn't snapping together as easily as it looks on the video.