Ok, this is my first post here…I’ve been using Blender for a while now but I just signed up here yesterday. Ok, both questions are about the rigid body physics. After much trial and error, I created a large rigid body block tower, and then ‘threw’ a ball at it so it crumbles. Fun. But, I want it to be in slow motion and I can’t figure out how to do this. I could attempt to select each of the 700 blocks and scale their curves in the ipo editor, but, you know that would take a while. Is there are easier way? My second question is: If I can’t build a stable rigid body tower to knock down, is there a way to ‘freeze’ it until the ball hits it so It doesn’t crumble right away? It always bounces and falls at the start…Is there any sway to build a tower that doesn’t fall as long as it is physically stable? (I try to build a physically stable tower but it bounces right at the start and fall? Sorry for the long post, and thanks for any help in advance! 
You could reduce the value of gravity in world settings. This won’t give you slow motion exactly, the blocks will still experience a “real speed” impulse if struck by a missile or another block but they will fall more slowly. If you have other objects in your scene that you want to experience normal gravity you can give them a world z force with an always sensor.
If your tower is bouncing when your sim starts it might be that the bounding boxes of your blocks are a little bigger than the blocks. Make sure you have zero margin selected and that your blocks are accurately placed in object mode so there are no intersections. A single block out of place can cause your tower to bump and fall at startup.
Thanks, just tried that and it looks pretty good! In object mode I had been placing my blocks by hand, but this time I placed them in perfect blender units so I works a lot better! Unfortunately with my new block placing method I was placing them so fast my computer crashed when I tried to bake the physics to ipo! Oh well…Thanks for the help!