Need help: game not working on Macs

I’ve developed a game (still a work in progress but won a contest with it already) that runs great on PC’s, but I’m finding that people with Macs simply can’t play it. My understand is it runs, but they can’t place the letter tiles. The game is located here:

http://www.trollbreath.com/AlphaCraft/AlphaCraft.html

If you have a Mac, please attempt to play the game. Try and click to place the tiles. Hold the mouse button down for several seconds and see if it will lay the tile then.

If you’re an actionscript programmer familiar with Mac issues, some clues as to what I may be doing wrong would be helpful. The code is way too long to post, but I can post select sections if it would help.

Thanks!