Odd RC.conf problem

[James]

I've set up a FreeBSD (4.6 Stable) server at home that's currently being
forced to gateway through a windows box until I've got everything else
working to my satisfaction and tackle PPP, but it appears to have an odd
problem.

When I reboot the machine, it loses it's Ethernet config and default route,
despite having the lines;

tl0_ifconfig 192.168.0.5
default_router="192.168.0.1"

...in rc.conf

At the moment I'm setting up the ethernet and default route up by hand after
rebooting, but I'd eventually like to leave the thing unattended in a
cupboard somewhere.