@nfoav8or:

It looks like you skipped the "update" command while using fdisk...
Here's what they taught me, and it's generally worked:

fdisk -e /dev/rdiskX (X=disk number)
update
f X (X=partition number)
w
q
reboot

Here's what that is actually doing:

fdisk -e /dev/rdiskX = starts fdisk utility in "interavtive" mode and selects the HD to use

update = "updates" the MBR ( Master Boot Record ) of the selected disk

f X = makes the indicated partition active

w = write = writes the updated MBR
(if it says here something like "cannot ... interactively, a reboot will be required... (Y/N)", choose Y, but you'll have a 50/50 chance that it'll actually work to make the partition bootable...)

q = quit = exits fdisk AND makes changes permanent

(you're now OUT of fdisk and back to a different command prompt)

reboot = just restarts your computer...

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Running both 10.5.8 and 10.6.4 on my stinking AMD/ATi machine...