How about just installing the stable (Woody) version of screen?..
You can of course go to http://packages.debian.org
and look for the package screen
in the testing (Sarge) section..
Click on the testing
link and check out the dependencies..
libc6 is listed, but you'll find a whole lot more dependencies are needed to install the testing version..
If you want to see how many, adjust your /etc/apt/sources.list file to show testing instead of stable, do apt-get update, and apt-get install screen..
Then change it back and do apt-get update to refresh the stable list..