They are still available.
What exactly are you clicking on? I went back to Jan 2009 and got a podcast. Steps I took
1. click Pjones1's link
2. click an archive - say January 2007
3. within the blog, clicked a link - episode 434
4. above click brings me to mrexcel.libsyn.com
5. click the pod icon and the episode plays in my browser or i can download it from the right-click context menu. There's also a direct download link within the post.