Ok I'm manged to make it work on a Cent OS 5.2 system so the same should apply to Redhat 5.x (Since they are the same base). I renamed my interface from eth0 to prod (for production network)
Here's some of my ifconfig output
prod Link encap:Ethernet HWaddr 08:00:27:4C:A3:53
inet addr:10.212.50.33 Bcast:10.212.50.255 Mask:255.255.255.0
Heres' how I did it, firstly rename the interface
1) Rename /etc/sysconfig/network-script/ifcfg-eth0 to /etc/sysconfig/network-script/ifcfg-prod
2) edit /etc/sysconfig/network-script/ifcfg-prod and change device=eth0 to device=prod
Now we must ensure that the system knows which hardware driver to use for our interface.
3) my modprobe.conf had the following entry, so I commented it out and created a new one
#alias eth0 pcnet32
alias prod pcnet32
This tells the system to use the pcnet32 driver and assign it to prod.
Finally reboot, and all should work.
Of course you need to change your modprobe.conf to reflect the correct driver, this is the driver used on my test system so would not work on yours.