networking curiosity

[david]

Greetings,

I experienced a small network problem today ad it's left me stumped.
I was installing 5 new Linux boxes into an office. The initial setup
being - static IP addresses and one folder set as shared for the others
to access vis nfs.
Four of the 5 machines took their IP addresses with no problem but one
of them kept saying "network unreachable". The first strangeness was
that I could ping the box that couldn't find the network from any of the
other four. Hmm, maybe it's the cable I thought and swapped it - still
no joy. (These boxes are all running Mandrake 10.) So, I whip out my
trusty Ubuntu live cd and boot up from it. Bring up the network
interface and lo and behold I could ping the other boxes. "Oh" thinks I,
"it must be Mandrake" (this project initially requires that Mandrake is
the distro of choice) so I reinstalled Mandrake and...
the same behaviour manifested itself. Network unreachable.
I know it's not the nic as I've installed a number of these Mandrake
boxes and had no problem with the networking side of things. I even
installed a 3com nic from another working computer and still the same
result. The boxes are all identical Evesham's and the hard drives were
all installed from a single master image - identical setups).
So, it's not the nic, or the drivers, it's not the cable nor the
existing network hardware so...
Why could the ubuntu live cd use the nic correctly and not the installed
Mandrake?