Uninstall Mandrake's Mozilla RPMs. If you don't know how to do that, go read up some documents on how to use RPM to manage packages. An understanding of package management is a key admin skill for Linux.
If you don't mind the download time, I would try Mozilla's Red Hat 7.x RPMs. They work fine on SuSE Linux, and since Mandrake is a closer cousin to RH, they should work fine on any modern Mandrake as well (modern meaning 8.x).
There's nothing wrong w/ the Mozilla net installer, but RPMs are a snap to use when they work.