RJL,
I had the exact same problem with Mandrake and RedHat. After 2 weeks of wasting time with both distros I finally gave up.
The GUI's in both RH and MD just DON'T work correctly especially if you install a third party application like a firewall. I got the ICS working in MD and then turned on the firewall with one of the MD control panels and it killed my ICS.
These type of behaviors were totally unacceptable to me. I wasn't trying to do anything fancy. I just needed a print/file/web/mail server with ICS and a firewall. I was trying to replace an MS server in a running business.
I built a new box and was ready to give Linux a try. What a disappointment and a huge waste of time. I don't have time to continually tweak things (I don't understand most of it anyway). I just need to load and go.
Then I found a miracle.....The MS server replacement....Simple....Easy to configure....One easy to use configuration console...No frills distro called SME/e-smith.
I was loaded and configured in 30 minutes. Added users and transfered files in another 30 minutes. The server has been running flawlessly for over 6 weeks now. When I make a configuration change it actually works the first time. WOW what a concept.
If you need the linux box for more than just server purposes then this won't work. it has NO GUI's what so ever. You manage the server from a client hooked to the network with a web browser. But the server manager works very well. It even configures samba and works the first time.
Some people scoff at e-smith because nowhere does it mention the word Linux on boot or in the manager panel. But it works and I am happy to have found it. It's a TRUE replacement for MS Server and I can't complain about the price...