Did you edit /etc/rc.d/rc.modules at some point? If so, you need to find where you had it load the 3com module and comment it back out with a number sign. If that's not the case, remove /etc/rc.d/rc.netdevice which is the file that netconfig creates. As a last resort, you could build a custom kernel with just the module for your new network card, but this shouldn't be necessary although I generally do so because I like to customize my system. Good luck and let us all know how it goes.
