I have the S625X, which is a great little toy with all of its features, but after 6 months I only use the % of max heart rate and distance traveled. As I already had a cycling computer, it I were to do it again, I would get a more basic model and save some money.
The USB IR port is a royal pain. First off, go to the Polar site and make sure that you have the latest software. Then, if you still can't download from your HRM, try the following.
It may be black magic, but the only sequence of actions that works for me is to first use the HRM to calculate "OwnOptimizer", start the software, switch HRM to "connect", click on the green button, and then mate the IR window of the HRM to the IR device. Finally pray.
I find that without running OwnOptimizer first, there is no connection. This means that you can download only about 2x's per week, but that should not be too much of an issue. But it is frustrating, that the system does not work as advertised. Polar tech help is useless.
Marc, do yourself a favor and get the most basic HRM that will allow you to log your progress manually.