The intermediate to advanced lessons here are top notch. As for the Jam trck section not working for you, can I ask you to please leave a post with what OS you are using (Windows, Mac, Linux, etc.) and also which browser you are using, (Internet Explorer, Firefox, etc.) That may help us root out your problem.

Check out some of the lessons here. The instructors are great and the site owner expects the best quality out of these guys. Hell they expect it of themselves. It has really shown in the lessons they put up.