Re: why does this happen in my perfect OS?
the repository driver should install from x and then ask you to reboot if i remember correctly, so shouldn't require you to stop gdm and run from terminal an application. you should see no install interface except the standard package install one you see for all applications. theoretically it should be supported you could check with lspci or lshw if the ids compare with the one in the release notes. also there are thirdy party repositories in launchpad might want to check them too although probably not needed as legacy updates aren't so frequent (and just adress kernel/x.org incompatibilities)