Why won't Ubuntu Server 9.04 won't upgrade to 9.10?

Solution 1:

Probably too late but....

Changing jaunty to karmic and old-releases to releases gives 404 errors

This should be old-releases to archive

Solution 2:

This upgrade will not work at all!
From the ubuntu-security-announce mailing list (received last week):

This note is just to confirm that the support period for Ubuntu 9.10
(Karmic Koala) formally ended on May 1, 2011 and Ubuntu Security Notices
no longer includes information or updated packages for Ubuntu 9.10.  

Hence the 404's.
"Cruel workaround": replace all "jaunty" 's in /etc/apt/sources.list and /apt/sources.list.d/* with "lucid" and run "aptitude update && aptitude dist-upgrade"