The regular tulip driver in 2.2.16 in its (semi) unique dual nature as a pci/pcmcia driver successfully drives the Ambicom cardbus ethernet adapter. However in the rawhide 2.4.0-0.99 kernel, neither the tulip module or the xircom_tulip driver successfully detects this card in a Winbook XL2 laptop. There's also a complaint that a slot hasn't been successfully recognized with a suggestion to increase the setup_delay in pcmcia_core -- which, however, does not change the behavior. So there's some brokenness going around here.
I had the same problem with the 3c59x driver detecting my etherned card which used to be run by 3c575_cb pcmcia driver. What I have done is to turn off pcmcia support from the kernel completely, get the pcmcia-3.1.23 package and compile and install all the modules, then make sure the file /etc/pcmcia/config is the one that is for NOT using kernel pcmcia and that /etc/sysconfig/pcmcia has PCMCIA turned on. I still get some PCI messages that I did not get with 2.2.16 but all the pcmcia cards are detected...by the way my computer is DELL Inspiron 4000.