Binary package hint: update-manager
I am trying to upgrade from feisty to gutsy RC with the 64 bits versions.
I started with "sudo update-manager -d -c"
All begins well : it tells me there is a new version (7.10)
I press upgrade...
After a few operations, I tells me that some packages aren't anymore supported,
Then it tells me that my system is up to date, no updates are available.
I finally found that it was because of my /etc/apt/preferences where I had given a low priority to gutsy.
Update-manager should at least warm stunned users about this.