I think I figure this Mandrake 8.2 / NVidia thing!
It is due to the fact that MAndrake will install XFree 3.3 if your
graphics card was not detected as having an XFree 4 driver
(this will happen to us GF4 users). The thing to do is to get it to
install Xfree 4 for another graphics card, without "testing" the
card. I used "xdrakconf ", selcted plain "GeFOrce" graphics card, pressed Advanced Mode, and selected Xfree 4. THen, without testing, logout of X into console mode and install the NVIdia RPMs.
This time they will find all the required XFree components and links. ANd the X link to XFFB_dev should dissapear.