the rpm -q system-config-network system-config-network-1.5.93-2.fc10.noarch saves incorrect data to /etc/sysconfig/network-scripts/ifcfg-eth0 The NETMASK field gets value of IP address or gateway. Thus the static eth0 interface created by system-config-network is unusable. Only manual edit of /etc/sysconfig/network-scripts/ifcfg-eth0 and setting NETMASK=255.255.255.0 can make interface working.
The problem is somewhat worse than described. If the ifcfg-ethX file is hand-edited, and system-config-network is re-run, then the netmask field is once again mis-set and the machine is effectively taken off of the network. Priority on this should be changed to *high*, because this will break connectivity for every unsophisticated user who is configured using static IP. I haven't looked at source for this (traveling), but this really smells like somebody made a sloppy two line change somewhere and didn't even make a casual test.
*** This bug has been marked as a duplicate of bug 469434 ***