up2date - whether run from cli or gui, polls the server for the mirror
to use to obtain updates whereas yum has to be configured for exact
repositories.
There are times when up2date will be told to use a mirror and that mirror will time out or for some reason be unavailable and this is not predictable. This can usually be solved by closing out all of the up2date gui windows and starting again (it will poll for the mirror to use again and hopefully will get a new assignment).
Since yum uses only the specifically designated repositories, you will see if it/they fail immediately, thereby giving clue what is wrong and thus, is easier for this list to dissect.
When you use the up2date applet, you are not seeing the totality of the problems (my guess is that they are logged in /var/log/up2date)
The default FC3 install of yum also uses mirrorlists. However, there is not (yet) a properly integrated GUI for yum in FC3, though this may be fixed by the time FC4 appears.
Paul.
