I seem to have found the cause of my network issues. It appears that the CentOS 5 kernel is not handling shared IRQs properly. My USB keyboard and mouse were on the same IRQ as my ethernet controller. Initially, the network would be working, but as soon as there was keyboard or mouse activity, the network stopped. After that the network would only work if the keyboard or mouse was active. Moving the keyboard and mouse to a different USB port seems to have completely cleared up the problem. Good and bad dmesgs at URLs below. Mark http://www.cs.wisc.edu/~nejedlo/dmesg.good http://www.cs.wisc.edu/~nejedlo/dmesg.bad