Hello everybody, I already posted the message in the "Driver, Kext" section, but this one seems more appropriated, sorry.

My PCI Airport Card, recognized as third party by System Profiler (it's a Belkin model, can't tell you the chipset right now), doesn't work when my rig has 4GB of RAM installed. If I pull off just one of the four 1GB stick reverting to 3GB or 2GB, everything is fine.
I'm not an expert at all, so I thought of something related to a 32 bit - 64 bit kernel or driver issue, as in Windows, like: to support 4GB Snow Leopard switch automatically from a 32 bit to 64 bit kernel and the 64 driver for the AirPort card doesn't work. I guess it doesn't make sense, because that's a Windows issue. And actually forcing the 32 bit kernel (checked the "64-bit Kernel and Extensions: Yes/No" description under "Software" section in System Profiler) hasn't solved anything.
By the way, I'm on a Gigabyte P35 motherboard.