Awesome, you finally got it working
I played around with it a little, it seems to be pretty solid, other than the tower glitch you mentioned. Just one thing though, now that the level is more complicated it's harder to discern where the blocks actually are. Maybe you could do some different lighting on them to help readability? Something like this maybe:
<img src="http://i37.tinypic.com/280jfw7.jpg">
Just a thought. Orthographic views can be kind of confusing sometimes.