There seems to be an issue with Firefox 184.108.40.206 and iTunes 7.6 on OS X with regards to M3U files. I've noticed this issue with eMusic as well. To solve this, I've included the URL of the actual streams, and if you enter that URL in Advanced --> Open Stream, that should work. There's also this script, but I haven't had a chance to try it yet.
Note: This problem seemed to resolve with iTunes 7.6.1.
Mitch Mitchell Dies at 62; Drummer for Jimi Hendrix (NYT) He was the last living member of The Jimi Hendrix Exerience. I always thought Mitchell was underrated for the musicianship on the "Are you Experienced?