Hope you weren't doing it to try to get a higher frame rate....29.4 is basically capped for FFXI (hard cap is 30). Especially if you are in Win7/Win8. If you are in XP....then most likely you will need older drivers, unless the newere ones are supposed to specifically be addressing the issues with older DirectX games like FFXI and such.

Unless you have a specific reason for it (like a bug fix for another game)---have you tride reverting to previous version?

New drivers have always been a problem with FFXI... newest isn't always wise. Same goes for newer GPU's---there are ongoing threads at each of the GPU sites--ATI, nVidia, and Intel--regarding the last few generations of products and FFXI/DX9 games in general.

Also.. did you do a full removal/cleanup of the drivers before installing different drivers? Could have some leftover files/registry entries causing issues.