Version:           unspecified (using KDE 4.4.95) 
OS:                Linux

The undo system seems to be broken. In a game me/black vs. computer/white I found some odd behaviours:
1) Once I undid a move, resulting in the last move on the stack being black. I was able to make a move, resulting in black having two moves in a row on the stack.
2) Once I undid several moves in a row, which apparently confused the computer: It did not make any more moves.
3) Pressing redo after undo will result in the computer (white) making a move (giving it two moves in a row), instead of putting back the black move. This one is perfectly reproducable.

Reproducible: Sometimes