may not all the time see the upgrade in your update manager. But you still want to upgrade to a newer version of the Ubuntu operating system. For instance Ubuntu 10.10 is the current Ubuntu operating system at the time of this righting. though you want to upgrade to the current beta for 11.04. well this is done simply by going to command line
sudo update-manager -d
this code will check to see if there is any new updates for your operating system and distribution updates.
The command is useful if you always have to have the newest things before everyone else and don't mind a bug or two in what your using because you have the newest and the best OS out there.
well I hope that you go out there and help test the new Ubuntu OS and help give back to the open source community.
local tech repair
Ubuntu 11.04 Crash after upgrade or update Nvidia drivers