Slow LAN /w 2.4.3

Hi, I've just switched from kernel 2.2.16 to 2.4.3 (because of a smbfs
bug). Anyways, all is well except for one little thing. Over the LAN in
2.2.16 I was getting around 900k/sec between the linux server and the
rest of the computers. After I upgraded I only get 200k/sec. I've
rebooted using 2.2.16 and all the sudden I get 900k/sec again. So, does
anyone know what's going on?

I've got two nics (Realtek PCI - External INet, Ehterlink III ISA -
LAN). I'm running Redhat 7.0, as well as ipchains.

Thanks,
  Matt