Hi Ben
I have used FC4, it is a fantastic distro. The only thing I can think of is either a service is failing to start and is holding bootup, or there is a problem with your X/Window Manager configuration.
First of all, try flicking between all your virtual terminals to see if anything has errored. If any services have failed, then this could be your problem.
Failing that, log in to a terminal (not X) and check your startup log files for any errors which may be relevant. If this doesn't work, check all your config files for X and your Window Manager (default is Gnome I think with Fedora).
The only other thing I can suggest is that you try posting in the
Fedora Forums. The people there are very knowledgeable and friendly and have helped me on several occasions.
Keep me up to date! :-)
--
moto