I found this information on another post. This is not the fsck -fy, but a derivative. Please try this out and see if it helps.
Boot off the OS X CD (reboot, hold C while booting).
The installer will load up, go to Utilities in the menu and run Terminal.
Type df and look for the drive that has your Mac system mounted---you'll have to unmount this. On my MacBook Pro, it was /dev/disk0s2.
Type umount /dev/disk0s2, replacing disk0s2 with whatever disk your OS lives on.
Type fsck_hfs -r /dev/disk0s2. If you umounted the wrong thing, it will complain that you can't repair a mounted drive. Go back and umount the right thing and repeat this step.
I have done a little digging and several posts on the Apple boards state that you will see that error anytime you run disk utilities from a live OS. It is not the error that is concerning as much as any stated issues in RED.
You did not mention if this is Tiger, Leopard or Snow Leopard. But as long as you use the OS-X CD/DVD, that should be fine.
I hope this is helpful.