problems getting ip with dhcp

[Andreas Kägi <andreaskaegi@gmx.ch>]

hello everybody,
i have a computer with two 3com-network cards, using the kernel module 3c59x. 
the first nic has a static ip-adress that works fine. on the 2nd card i have a cable-modem, and want to get the ip-address via dhcp. so i have set the /etc/network/interfaces to:

auto eth1
iface eth1 inet dhcp

but eth1 does not get a ip-address assigned. ifconfig -a shows:

eth1      Link encap:Ethernet  HWaddr 00:04:75:E5:51:0C
         BROADCAST ALLMULTI MULTICAST  MTU:1500  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:100
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
         Interrupt:11 Base address:0xb800

ifconfig without the -a option doesn't show eth1 at all.

i don't know where the problem is but i think it cannot be the modem since i tested it on another box with both windows and linux. 

i have few experience with linux and such networking issues and would be glad if somebody could help me.
i've tried alot and read several howtos but couldn't find any information on that specific problem.

andreas