Perolo Silantico [off-list ref] :

Same behaviour for drivers:
  - 8139too (kernel 2.6.8.1 and 2.6.8)
  - e100 (kernel 2.6.8)
  - eepro100 (kernel 2.6.8.1)

I have tried with all these drivers. Therefore it seemed to me, that
this is not related to any specific driver. But to be sure, I will
grab a 3com 905C from another server and try with that one and will
try with the PCNet32 too.

Can you give a try to 2.6.7 for the 8139 setup ?

A dmesg from a working 2.4.x may help figure some difference.

--
Ueimor