You can try putting the card in promisc mode 

Forum: Xircom PCMCIA Ethernet Adapter Issues
Re: No network using Xircom RBEM56G-100 (Stuart Pedler)
Date: 2000, Aug 25
From: David Hinds <dhinds@pcmcia.sourceforge.org>

That work-around is mentioned in the BUGS file. -- Dave

to: "You can try putting the card in promisc mode"