If its a mission critical system, I suggest that you don't upgrade for now (unless there is a feature in FC4 thats really really critical to your task)
also, can you add a comment on that bugzilla place and tell them about your hardware specs? It will help Fedora improve so that this wont happen on your hardware again. (you need to create an account with them.)
PS: If you really need to update, search for a how-to on how to upgrade to FC4 using YUM.
Patience is the key to Linux......