[I enter]

#sudo apt-get install cvs

[output]
.
..
[bunch of lines, all sound pretty positive]
...
....
Need to get 1646kb of archives. 
Err http://us.archive.ubuntu.com edgy/main cvs 1:1.12.13-3
  Temporary failure resolving 'us.archive.ubuntu.com'
Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/c/cvs/cvs_1.12.13-3_i386.deb 
 Temporary failure resolving 'us.archive.ubuntu.com'
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

[wondering what's wrong? apt-get works fine for other packages]