I have recently bought a DELL 510 M. Mine was delivered with a wireless card with a Broadcom chipset. This chipset is not recognized by Linux.
I had to install 'ndiswrapper' (have a look on sourceforge.net) to be able to use the Windows driver under Linux (Mandrake 10.1).
The specification on my card are :
Vendeur: Broadcom Corp.
Description: BCM94306 802.11g NIC
I do not know which chipset is installed but it could be interresting to investigate that option and possible explanation.
Hope this helps,