My IBM A21p came with a 3com 3c556b mini-pci combo card. Its never worked all that great with linux. Not that I've ever used it all that much, the 3com modem is completely unsupported by linux (way to go 3com, I love you). I was able to accept that because god forbid I'm not always on broadband :). The ethernet card on the other hand worked. The kicker was that I always had to disable acpi with acpi=off on all my linux installs for recent 2.4 and the entire 2.6 release since the test versions. NOW, the most recent versions of the linux kernel break REGARDLESS of the acpi parameter.
I did some poking around and found out that you can easily replace these pci cards and I knew that some versions of my laptop (A21p 2629, mine is the HWU version) came with an intel ethernet/lucent modem combo that works great with linux. Sure enough, according to ibm's website there are a few different cards that are field replaceable in the A21p line (and many other lines for that matter). Over to ebay and in 10 minutes I've got a used 06P3809 (ibm part number) mini-pci combo card ordered and it only set me back about $20 bucks shipped.
Installed it today and suprise suprise, it works flawlessly. I haven't tried out the modem, but all reports seem to indicate that it works fine. I guess none of this changes the fact that this broke completely between a STABLE release of linux. Oh well, sucks to be me. Atleast now I don't have to dick with the acpi=off thing.