Yeah, I think your GRUB boot loader is busted. It sounds like you may have upgrade-installed from Fedora 9. Anyway, it happens often enough. I agree with your desire to manually boot the system from that grub> prompt, but you can't just enter "boot" as you found out. You must do that after a couple of other commands (e.g., root, kernel, and initrd). For example, starting with the root command at the grub> prompt...
You change x & y to the drive & partition of your boot partition where the kernels, initial ramdisks, and GRUB files are located. If you aren't sure of it, then you can find it like this...
grub> find /grub/stage1
grub> find /boot/grub/stage1
Do both. One will produce an error, and the other will identify your boot partition. Use that in your root command. Continuing on...
Next is the kernel command...
grub> kernel /vmlinuz-[version stuff here] [parameters here]
You can usually get that kernel version information using the Tab completion feature of the GRUB shell. Type that command through at least vmlinuz and press the <Tab> key to see the options available to complete the command. Continue that process until you have the complete kernel version typed in. You can probably stop there and it may still work, but if you know the root partition you can enter that after the version (e.g., root=/dev/sda2 or whatever it is).
Next is the initrd command...
grub> initrd /initrd-[version stuff here].img
Fill this out with the help of the Tab completion feature also.
NOTE: The kernel and initrd command examples above are for when the boot partition is a separate partition. If you do not have a separate boot partition, then you must include /boot in the path of the the kernel and initrd commands. Put it in front of the /vmlinuz and /initrd part.
Now enter the boot command...
Hopefully it boots. Then you can go about the business of repairing the GRUB boot loader for whatever is making it do this. Look for obvious problems in the grub.conf file. That is the classic reason for landing at a grub> prompt. You may also need to re-install the GRUB boot loader. That is not uncommon.
Lastly, if you never get anywhere with the above, then consider downloading a Super Grub Disk
. It's a free utility that can boot a GRUB-booted Linux system when the only thing wrong with it is the boot loader. There are versions for CD, USB, and floppy. It would be a simple way to confirm that the Fedora system is capable of booting in the first place. The Super Grub Disk is not a pretty GUI app. It a dull-looking text-mode menu-driven utility. And it's menus can be somewhat maze-like until (like anything new) you learn it. But in spite of all of that, it's a very handy thing to have around. There is documentation help either on the disk or at that web site. It works by finding menu.lst and grub.conf files and launching them configfile-style. But it can also directly launch the kernel and initial ramdisk (direct method) in case the menu.lst or grub.conf is missing or bad (maybe why you are landing at that grub> prompt). So if one method fails, try the other.