Where you have added developers PPA's (Personal Package Archives) and other third party sources, you should check in Software Center that they still have check-marks enabling them, otherwise you'll get no more automatic updates from them.
There may be a good reason why Ubuntu has disabled them; check the distribution version and update any older package sources to match Oneiric or 11.10.
You should check the exact archive name and update the sources line for the new version.
You should also then run a:
sudo apt-get update
in a terminal to make sure the package list for those sources is refreshed. RC