Fedora Core 10 cannot set static ip address

[stephen]

When you use the gui system-network-config to configure a static ip address
The confirm screen changes the netmask to the gatway ip address.
it does not accept 255.255.255.0 as the subnet mask, and it instantly changes back to your gateway IP

This is reported as a bug here
https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/178775