Transmission hangup after long periods without link

I'm using V1.20a of rtl8139.c on a Celeron 850-based motherboard with 
two 8139C Ethernet adapters. The box is running Redhat 7.2 with a 
2.4.7-10 kernel. We are using this box as a router (both unicast and 
multicast) and it has run successfully with a 6 Mbps data stream for 
days at a time.

In our configuration, traffic goes through the box in one direction 
only. We discovered that if we unplug the Ethernet cable on the outgoing 
interface and leave it unplugged for some period of time (12 hours 
usually does it) and then re-attach the cable, no data comes out. 
rtl8139-diag shows that the link has been detected. Tcpdump shows that 
braodcast/multicast traffic on the outgoing interface's cable is being 
received but that there are no outbound packets.

If we then use ifconfig to bring the outgoing interface down and back 
up, output resumes immediately. I turned on debugging when I installed 
the driver and all I see are abnormal interrupt messages when the link 
status changes.

Any ideas? This problem is sort of obscure, but it's the kind of thing 
our customers tend to do, especially during system installations. I 
tried to reproduce this problem with the 8139too driver. It causes 
kernel panics at about the same rate as output stops with rtl8139.

Regards,

Scott Henwood