Problems with a Scientific Linux 3 smp kernel on a Tyan Transport GT24 (B2891)

Hi there,
we try to use a SL3 (32bit) smp kernel on a Tyan Transport GT24 (B2891),
Chipset NVIDIA nForce4 Professional+ with 2 dual core Opteron processors.
We observe that neither the onboard network cards (broadcom chip BCM5704)
nor external network cards seem to work. We do not see any error message
in /var/log/messages. We tested both drivers tg3 or bcm5700.
Compiling the latest kernel (2.4.32) does not change the situation.

The single processor kernel of the 2.4 series and smp kernel versions of 
the 2.6 series seem to function properly.

Are there any solutions?