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