Does your mac meet any of the minimum requirements in this link? Optimizing Your WGT Experience
I play on a mac and mine actually doesn't meet every requirement. I only have 1 GB RAM and I'm pretty sure my processor is just under 2 MHz, but I do have Flash 10. Maybe that's your problem? Check your popup blocker as well. If you're using Safari click on the Safari menu in the top left corner. If there is a check next to "Block pop up windows", click it and pop-ups will no longer be blocked.
Hope either of those solves it.