Make sure sources are enabled and you have contrib and non-free enabled in /etc/apt/srouces.list and include the unstable branch with squeeze.

deb http://mirror.its.uidaho.edu/pub/debian/ squeeze main contrib non-free
deb-src http://mirror.its.uidaho.edu/pub/debian/ squeeze main contrib non-free

deb http://security.debian.org/ squeeze/updates main contrib non-free
deb-src http://security.debian.org/ squeeze/updates main contrib non-free

# UNSTABLE
deb http://mirror.its.uidaho.edu/pub/debian/ unstable main contrib non-free

Now update apt.

as root:

echo ‘APT::Default-Release “testing”;’ >/etc/apt/apt.conf.d/00defaultrelease

aptitude module-assistant linux-source-2.6.30

apt-get -t unstable install fglrx-control fglrx-driver fglrx-source

m-a a-i fglrx

aticonfig –initial

restart X or reboot system