Hello Neil,

   NL> I've got a Satellite Pro 445CDT that wedged reliably
     > with a combination of 64M memory upgrade, 10/100
     > cardbus ethernet (3-Com Megahertz), and XFree86.  To
     > make a long story short, it's now running fairly
     > reliably with the ethernet configured to 10Mbit (one
     > lockup while tunnelling X over ssh).  My guess is that
     > the fast ethernet uses too much memory bandwidth and
     > interferes with memory refresh (heavy network usage in
     > text mode would corrupt new output before crashing).

I don't think that's quite it (although it may be close).
I'm connected to my trusty Netgear EN104TP four-port 10baseT
hub, so it doesn't try 100MB/S: The 100M light on the NIC
remains unlit.

   NL> PS - I can forward dmesg and X logs if you're
     > interested in comparing working hardware.

I would be interested in seeing that.

Thanks,
   - Andy Ball.