Can't find cable internet connection

["Edward C. Jones" <edcjones@comcast.net>]

I use Debian unstable (i386 port) on a PC with an AMD Athlon 64, 3500x 
chip. Debian is up to date as of about 5/15/07. I get the Internet over 
a cable modem.

For the last two days I have been unable to access the Internet. When I 
reboot with an old Kanotix live-cd, the Internet is accessible. How do I 
go about diagnosing what the problem is? Any troublesome package 
upgrades recently? Any idea what the problem might be?