Try this one:
Code
- deb http://ftp.de.debian.org/debian stable main contrib non-free
- deb-src http://ftp.de.debian.org/debian stable main contrib non-free
- deb http://ftp.debian.org/debian/ squeeze-updates main contrib non-free
- deb-src http://ftp.debian.org/debian/ squeeze-updates 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