AGS Tetris Clone

A few friends and I are making a tetris clone, and we badly need some help on the following bugs:

1) pieces solidify as soon as they touch the ground
2) sometimes parts of falling pieces will dissappear
3) when moving the piece, the falling piece blacks out momentarily
4) the screen flickers massively, even though we attempted to implement double buffering early on.

any help would be appreciated more than words can state. the code can be found at www.antithesisgames.com/main.cpp and www.antithesisgames.com/main.h

note: the version that is up at the time of this writing does not even permit the pieces to fall due to a failed attempt to fix the solidify function.

additional note: those of you which would like some background information on how this (terribly buggy) version of tetris was formed, visit www.subduck.com, where we have a gigantic thread called "making tetris"

Wow. I hear all these grand tales about the knowledge of the people at this site, and not one of you even bother to look at my post. I'm hurt. :(