Functioning System Fails to Boot

[Richard Heck]

My system, F16, was working fine yesterday, but today refuses to boot. I 
just get a flashing cursor. I'm guessing the bootloader has somehow 
failed, so I googled around for this and tried several variations of:
     grub2-install --boot-directory=/mnt/t /dev/sdb
which seems right: the /boot directory is mounted at /mnt/t, where I've 
booted from an F16 install disk, and I've tried /dev/sda, too, and 
everything else.

After this, I get a grub boot screen, sort of, if I select the right 
drive in the bios boot sequence (F8), but then i get:
     Error: no such device: 440025921-.....
which is the UUID of /dev/sdb2, as reported under the live CD. So it 
seems as if it's not finding /dev/sdb2. And then it dumps me into:
     grub rescue>
which seems wholly useless, since such things as:
     ls (hd1,2)
report: no such partition, even though it's there.

Help? Short of re-installing?

Richard