Oh yes, I should have thought of that, since I have helped at least two others with the exact same solution... =)

The fact is that Windows doesn't release its DHCP lease when it shuts down, and therefore you need to do that.

Linux normally releases its lease, it just hasn't done that now since you followed my advice and invoked the DHCP client manually. However, use Redhat's network configurator (under the program menu, "System Settings" and "Network") to set the card to DHCP instead, and it will work the next time you boot into Windows. That will also make it work automatically in Linux, so that you don't need to run dhclient every time you want out on the net.

However, I cannot help you fix the fact that Windows doesn't release the DHCP lease, since I know virtually nothing about Windows. If you don't find a solution to it, you'll have to run "ipconfig /release" every time you shut Windows down.