I tend to have quite a few problems with YUM myself, if you want to use apt/synaptic it is quite easy(and I think nicer with a GUI), I use the following /etc/apt/sources.list file:
rpm
http://ayo.freshrpms.net/ fedora/linux/3/i386 core updates freshrpms
rpm
http://apt.atrpms.net/ fedora/3/en/i386 at-stable
rpm
http://wftp.tu-chemnitz.de/pub/linux/dag/ fedora/3/en/i386 dag
rpm
http://wftp.tu-chemnitz.de/pub/linux/dag/ dries/fedora/fc3/i386 dries
Don't forget to import the keys for each of these repositories if you use them this way as well.