Are you running Woody or Hoary?
If you are running Hoary (or would like to upgrade)...
Check you /etc/apt-get/sources.list and make sure it looks like this then
sudo apt-get update && sudo apt-get upgrade
To get the most up-to-date packages.
If you're running Warty, you could add the warty backports repository to your sources.list. Search this forum or google for 'warty backports' to find out what to add to your sources.list. After you enable 'backports', then 'sudo apt-get update && sudo apt-get upgrade' should do the trick.