I've the same problem. I'm also using Ubuntu 7.04, kernel 2.6.20, but as the sounddevice a nvidia soundstorm (nforce2).
The problem is also described here:
http://www.via.ecp.fr/via/ml/vlc/2007-03/msg00019.html
Thanks
Could you upload them again to ftp://streams.videolan.org/incoming ?In the file i've uploaded on your server months ago you can see this behavior.