might be your problem. As mentioned earlier, this is an issue dating back as far as the 400 series. Note the emphasis on the word "series". Try searching for solutions within each family, not just the specific card number. The problems actually date back further than just the NV400 and ATI 5x00 series cards, as all three brands have gone through phases where certain families of cards and/or drivers mysteriously go bonkers with FFXI (ie the 169.xx drivers from nvidia, ATI's Catalyst 9.x series...issues keep returning to bite them in the butt).
Some of the more common tweaks that have worked for some were diabling shadows, Catalyst AI and such, but in most cases the vendors had to release drivers with specific tweaks to fix issues. I recall there were specific threads in the 400 series section at that nVidia site addressing issues with FFXI/FFXIV that resulted in nVidia working with players to come up with a series of beta drivers trying to fix it, just dont' recall if they ever nailed it down though. Considering how laptop GPU's often modified versions of older desktop chipsets (some ATI's actually take bits and pieces from multiple designs, so the number doesn't actually align with the desktop numbers)--there is a strong possibility an older driver will contain the fix you need.
Alternatively, you could do as many others did with the Optimus design....run FFXI on the Intel HD Graphics. But again, some of those on-die GPU's need a specific WDM release to run it properly. This was also covered at the Intel community forums as well. I posted a link to a thread on the Intel issue a few weeks back.
At work ATM, so can't really dig much...if I get a chance later to dig up the links for NV400 series and the HD4000 threads and edit them in later.