As I seem to have major issues using my
DELL WLAN 1350 minicard to connect to any wpa-based connection as it doesn't seem to be supported, i have no other choice but using the wifi-stick that's not being used at the moment.

At home we work with WEP and this works... but at school with wpa-enterprise things all go wrong.

Is there a way to disable the wlan minicard in linux since the nm-applet seems to recognise both but won't let the stick work without the wlan minicard being enabled, which is a pain in the ass... because if the wlan minicard tries to connect, kubuntu crashes.

I'd rather not disable it in the bios as i still wish to use it in vista...

Presumably they are not using the same driver (since one is on the PCI bus and the other on USB), so you could blacklist the module for the internal card. Figure out which module the device is using with lsmod, and add it to the blacklist file.

The general idea is covered pretty well here.