USB modem troubles

I've got a USB modem that I'd like to get working, but I'm having trouble with it. It's an ELSA Microlink 56k Fun USB (hmm... Fun!).

I'm using linux-2.4.20 in Gentoo, and according to the docs for the "acm" driver, by compiling the acm.o module and installing it, I should get a few device files in /dev/usb (thanks to devfs). I also ought to see things in /proc/bus/usb. /dev/usb is empty, and /proc/bus/usb doesn't even exist! dmesg shows no errors. Oh, I just did make menuconfig, make modules and make modules_install - I assume a new bzImage isn't required?

I've got usbcore compiled into my kernel, usb-uhci installed as a module (and being used by my USB mouse without a problem), but it's not working. I tried creating the device file myself as suggested (mknod /dev/usb/ttyACM0 c 166 0) but cat'ing it just gave me "cat: /dev/usb/ttyACM0: Invalid argument), so that obviously wasn't any good either.

Has anyone either got a USB ACM modem working, or any advice on what to do? Btw the docs for acm are found at /usr/src/linux/Documentation/usb/acm.txt (or wherever your kernel sources are)

All I get from googling is that the standard version of the modem is known to work, but nobody on linux-usb has tested the "Fun" version.

Btw, if you are using Gentoo, I can really recommend that you use the ck-sources (emerge ck-sources) kernel. It's much faster than the vanilla one.

I think you also need Preliminary USB device filesystem enabled (I needed it for my USB ADSL modem).
And I assume that you have /dev file system support (EXPERIMENTAL) and Automatically mount at boot enabled?

I've got devfs support in, as well as USB filesystem (I think, from memory, because I set it up for my digital camera, which would make sense).