OS X Chess

I've been playing a lot of chess lately. The "Crazyhouse" chess game in OS X is great...chess with the element of surprise. Basically, as you take you opponent's piece, it goes into a holding area where you can then put it back into play--for your team! It's a cool concept, it's just too bad that the Chess application is still buggy even in 10.4.11. For example, make a bad move and hit undo (Take Move Back), the computer will continue to move. I've had the computer put invisible pieces into play numerous times and have lost to these invisible piece several time. Fair? I think not!

Have you experienced these same bugs?