> errors when I start "sh netstart" and in startup. It says "Invalid
> argument" on those lines in "ipnat.conf" and "ipf.conf".

This might be utter nonsense, but in a similar situation I got errors 
when I was configuring the interfaces. Cause was a media selection I
copied from the old ifconfig.??? which was invalid for the rtl8139 card,
causing the ifconfig to fail. Might your error result from a similar
case (and hence, for ipf, an unknown/unconfigured interface name)?

Hope this confuses the issue further,

Martijn