"RPM is a wonderful invention in that it makes installation of binary packages so much easier. The only downside is the cascade of dependency problems that can occur."
Absolutely true, however your solution is effectively doing things "the hard way".
The correct way to do things in Mandrake is to let URPMI do all the work for you.
That is first set up the URPMI sources as documented here:
http://www.zebulon.org.uk
then from a root console
urpmi pips-sprx500_510-cups-2.6.2-1.i386.rpm
and watch the "magic".