[thaumaturgy]

squeeze-lts is only available for i386 or amd64 architectures, I think, or you might be hitting an out-of-date mirror. You might try http://mirror.cc.columbia.edu/debian/ instead of http://http.debian.net/debian/

[lemming]

Using Columbia didn't help either. Using uname -m shows x86_64 so I guess that's it. I'll just have to wait for another update.

[thaumaturgy]

Silly question, but did you use sudo for the apt-get? I forget to do that sometimes. Because I'm a bit stumped why you're not getting the update, you should be.