WPA2 seems to work fine on my T42, using Intel 2915ABG (known to GENMAC as an 8086:4220).
It is probably one of the "edge" conditions that GENMAC runs into, sometimes. It may depend, exactly, how everything fits into the memory space that GENMAC uses. It is known, that some windows drivers will overwrite part of the GENMAC configuration area. Depending, exactly, what gets overwritten, something may, or may not, work. The only way to find out, for sure, is to try it.
*Gasp* well that's a relief! I'll just disable physical ethernet in the BIOS so that there's only one NIC connection (The wireless adapter).
Disabling the ethernet may, or may not, help (probably not, if you have the problem). Sometimes, changing some settings for the windows driver will reduce the memory footprint, but that can cause, as well as work around, problems. Personally, I don't care if WPA2 works, or not, so I haven't tried to fix the problem.
If you have the problem, and can't get it to work, one option is to use a device that does WiFi, when connected to the wired NIC. I use a D-LINK DIR-506L, which works pretty well, and it is useful for other things. It is also faster than a 2915ABG, but it is a few years old now, so you may need to find a newer device that does what it does. There are a number of them available, at pretty reasonable cost.