Also works fine for me in IE - WinME, JDK1.4.2, IE 5.5.
Level 19, 3,002,423 points. Got a lot more gold this time around, and still had 5 gold in the bank and two unused bonuses at the end of the game. Had 11 gold spare at one point!
One thing I’ve noticed is that a lot of the time I’m frustrated with the game. The problem as I see it is that while I need to look at the board to decide what to do, I then need to look away to aim my mouse at a (quite small) arrow to actually do anything. Frequently I miss the arrow because I can’t afford to take my eyes off the board, or I click the “wrong” arrow because the board moves when my eyes flick to the border.
As there is currently no functionality that requires clicking on the board itself, maybe you could include an alternative way of moving the board that way? Click a piece and drag it to move the monkeys in that direction, something like that?