is your linux box networked to any other computers? if it isn't then, next time you are able to boot into linux with no problems, try this:
"start--->System Settings--->Server Settings---->Services" when the "Services" program starts, look for "network" in the list on the left, uncheck the box next to it, save, and reboot, this will stop any network activity, like setting up a hostname, hopfully while FC3 is booting it will skip the setting up hostname stuff and you will be able to boot no problem.
if you are setting up a network with this computer then try opening the "Network" configure program, under:
"start---->System Settings----->Network" click on the eth0 card, and click on configure, in the configure box, insert an IP and a NETMASK, the netmask is pretty much always "255.255.255.0" if your FC3 box is the main server box (all other computers connect to it through a router) then you can set the IP to any IP you want, if it's being connected to a router (a client computer) then insert an IP starting with the IP of the router...so it would look somthing like this if you had 5 computers connected to a router:
click ok on the configure window, now back at the "Network" setup window click activate, it will say that the configure file is not saved and ask you if you want to save the file, click yes, and it will save the configure file and then activate the NIC, hopefully there shouldn't be any problems when activating the NIC. when this is done I suggest rebooting to test everything out.