I got the same thing with the 6629 driver, although it did give me an error that others did not include and may be useful:
Originally Posted by 6629 installation
Warning: Your kernal was configured to include rivafb support as a loadable kernal module. The rivafb driver conflicts with the NVIDIA driver. The NVIDIA kernal module will still be built and installed, but be aware that the NVIDIA driver will not be able to function properly if the rivafb module is loaded!
Is this of any importance? I can't get my hands on a cable now, but if this doesn't resolve, I will find and order a serial cable from somewhere online.
Thanks for everything.