1. Are you using custom compiled kernel?
I assume you are NOT.
When it doesn't work. Get the following output and post here
If you are not sure how to save the output, just add >> /home/lq_network_debug.txt behind each command. eg.
dmesg >> lq_network_debug.txt
Posting your /etc/rc.d/rc.inet1.conf and /etc/resolv.host would also help.