I've just installed FC6 which seemed to go well until i rebooted my machine. The boot up seemed ok but once finished instead of seeing the log in screen i get a blank screen with the message box " Analog RGB 15khz/14hz Out of range". I can't log in or indeed see anything so how do i solve this puzzle??

Switch to a terminal using <CTRL><ALT><F1..F6> and configure your X setup again (don't know the command in FC).
Next switch to the GUI using <CTRL><ALT><F7> and restart the X server with <CTRL><ALT><BACKSPACE>.

I've tried that before but once the boot up has finished no amount of key pushing brings up anything but a blank screen- no terminal, GUI nothing. I might have to try getting a copy of FC6 vfrom another source and reinstalling to see if that makes any difference.
Just incase i've not quite done things right, How do i get to a terminal once i've selected FC6 from GRUB, I've tried several times using different ideas but nothing helps so far.

My previous post was to let the system boot into FC6 and when the boot is completed press <CTRL><ALT><F1> (or F2 etc). If that did not work, you can tell grub to start FC6 differently.

When the grub screen appears, follow these instructions
No GRUB around here at this momnet, so I could not try it.

If RH/Fedora did not change too much since the last time I used it, you can pass 3 as the runlevel so FC6 boots in run level 3 (fully functional text mode).

Next you can login as root and make this change permanent (if you want to) by editing /etc/inittab and change the initdefault.

And now you should be ready to change your X configuration.

you installed the nvidia drivers didn't you -- silly boy.

if that is the issue, then its a common one -- nvidia + kernel 2.6.18 = does not play nice with.

solution = use stock linux NV3* driver than installs with FC.