The card is dropping interrupts
Xircom PCMCIA Ethernet Adapter Issues
Problems with cs-3.1.4 and Kernel 2.2.13 (Stefan Kapfhammer)
ttys* init (Philippe Henry)
RBEM56G eth0 timed out when used with ISDN modem (ipmasq) (Jean-Pierre Hermand)
Date: 1999, Nov 20
From: David Hinds <email@example.com>
It sounds like an interrupt sharing problem; ensuring that interrupts
are not lost when both card functions are in simultaneous use can be
tricky. This driver doesn't do anything special in this situation.
I'm not sure if/when it can be fixed.
Checking dropped interrupts by Stefan Kapfhammer, 1999, Nov 20
to: "The card is dropping interrupts"