Hi
if i was going to change the eth0 ipaddress via the web the first thing i would do is setup on of the virtual interfaces like eth2 with the current address 192.168.1.2
once that is applied logout of the web interface then connect to the new address (.2) then you can modify eth0 without lossing connection once eth0 and dhcp0 have been changed you can reconnect to the route on the new real address and clear the ip address out of eth2
hope that helps
James