When you click on 'free', the next page that opens should say "Download ticket reserved. In XXX minutes your download will be ready." about halfway down (XXX being a number that will decrease in time). When the countdown ends, you'll be asked to enter a letter/number sequence into a box. Do that, and your download should start. Good luck.
Yeah, what RTHTW said. They try to get you to go one of the pay routes, but if you "try again later" (the 4 minutes above is relatively short) you should be able to get through.
