Why network doesn't get initialized on system startup?

[Yuri]

I have two similar machines, on one rc.conf has:
wlans_ath0=wlan0
ifconfig_wlan0="ssid wifi-net-id weptxkey 1 deftxkey 1 wepmode on wepkey 
0x1234567890 DHCP"
and it gets initialized at startup.

On another rc.conf has:
wlans_ndis0=wlan0
ifconfig_wlan0="ssid wifi-net-id weptxkey 1 deftxkey 1 wepmode on wepkey 
0x1234567890 DHCP"
and this one doesn't get initialized at startup.

The only difference is that the second one uses ndis0 with some 
preloaded ndis driver. It shouldn't matter.
How can I make an interface to get initialized at startup and why it 
doesn't do this by itself?

Yuri