apt-get errors

[Jason Majors <jason@whizzird.net>]

When I run apt-get update I get this error:
    gzip: stdin: invalid compressed data--crc error
    Err ftp://http.us.debian.org testing/main Packages                             
      Sub-process gzip returned an error code (1)
    Fetched 1306kB in 10s (119kB/s)                                                
    Failed to fetch ftp://http.us.debian.org/debian/dists/testing/main/binary-i386/Packages  Sub-process gzip returned an error code (1)
    Reading Package Lists... Done
    Building Dependency Tree... Done
    W: Couldn't stat source package list ftp://http.us.debian.org testing/main Packages (/var/lib/apt/lists/http.us.debian.org_debian_dists_testing_main_binary-i386_Packages) - stat (2 No such file or directory)

Then when I try something like apt-get install dpkg I get:
    W: Couldn't stat source package list ftp://http.us.debian.org testing/main Packages (/var/lib/apt/lists/http.us.debian.org_debian_dists_testing_main_binary-i386_Packages) - stat (2 No such file or directory)
    W: You may want to run apt-get update to correct these missing files

I'm running a mostly testing (some unstable) box with:
apt   0.5.3
dpkg  1.9.15
gzip  1.2.4-33


On my box at work I have an identical sources.list, and the same versions of 
apt, dpkg, and gzip. On the server that's on the same network as this box, I
have older versions (the latest stable) of everything, and apt-get update works
just fine.
Does anyone know what's wrong or how to fix it?
Thanks.


The important lines from my sources.list:
deb http://security.debian.org stable/updates main contrib non-free

deb ftp://non-us.debian.org/debian-non-US stable non-US/main
deb ftp://non-us.debian.org/debian-non-US testing non-US/main
deb ftp://non-us.debian.org/debian-non-US unstable non-US/main

deb ftp://http.us.debian.org/debian stable main
deb ftp://http.us.debian.org/debian testing main
deb ftp://ftp.us.debian.org/debian unstable main

deb ftp://http.us.debian.org/debian/ potato main contrib