kernel-source packages are specific by kernel. If you have the 2.4.19-foo kernel, you'll need the kernel-source-2.4.19-foo package. Check a Mandrake mirror...
Can you check the md5sum of your Nvidia SRPMS against the posted ones on the driver page? You can check with 'md5sum /path/to/SRPMS'. The "missing binary operator" messages occasionally pop up on a bad download.