Fedora core 1 does not come with mp3 support in XMMS or any app for that matter, legal reasons. Do a search for that problem and you can find a link to the rpms to fix it.
What do you mean freezing in the middle of installing a package? AKA Rpms? I think I had the same problem, it does the little slider bar across a few time, and then it just stops at the end and the program hangs? I had that happen many times, I was forced to reboot to get it to run again. Perhaping using the 'rpm' command in the terminal for it may work. Try that. I do not know the exact syntax for it though, sorry.