I have a Thinkpad T42 with a wm GigE card.  I've never tried it at GigE 
speeds; it runs fine at 100 Mbps.  But it doesn't work at 10 Mbps if I 
have it set to 'media autoselect'.  However, if I set it to 'media 10baseT',
it works.  Here's some output; note in the first (failing) case that at 
some level it has detected that it's talking to a 10baseT hub.

I'm running 3.99.3 from about two weeks ago, if that matters.


# ifconfig wm0 media autoselect   
# ifconfig wm0
wm0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities=87<IP4CSUM,TCP4CSUM,UDP4CSUM,TSO4>
        enabled=0
        address: 00:11:25:43:e8:a4
        media: Ethernet autoselect (10baseT)
        status: active
        inet 192.168.7.117 netmask 0xffffff00 broadcast 192.168.7.255
        inet6 fe80::211:25ff:fe43:e8a4%wm0 prefixlen 64 scopeid 0x1
# ping -c 3 -n 192.168.7.77
PING 192.168.7.77 (192.168.7.77): 56 data bytes

----192.168.7.77 PING Statistics----
3 packets transmitted, 0 packets received, 100.0% packet loss
# ifconfig wm0 media 10baseT
# ping -c 3 -n 192.168.7.77
PING 192.168.7.77 (192.168.7.77): 56 data bytes
64 bytes from 192.168.7.77: icmp_seq=0 ttl=64 time=1.504 ms
64 bytes from 192.168.7.77: icmp_seq=1 ttl=64 time=0.883 ms
64 bytes from 192.168.7.77: icmp_seq=2 ttl=64 time=0.815 ms

----192.168.7.77 PING Statistics----
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.815/1.067/1.504/0.380 ms
# ifconfig wm0
wm0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities=87<IP4CSUM,TCP4CSUM,UDP4CSUM,TSO4>
        enabled=0
        address: 00:11:25:43:e8:a4
        media: Ethernet 10baseT
        status: active
        inet 192.168.7.117 netmask 0xffffff00 broadcast 192.168.7.255
        inet6 fe80::211:25ff:fe43:e8a4%wm0 prefixlen 64 scopeid 0x1


		--Prof. Steven M. Bellovin, http://www.cs.columbia.edu/~smb