You're THE MAN!!!
An hour ago got my BCM5752 (pci14e4,1600) working like a charm: MAC's - OK, DHCP's - OK, 100M/1000M - OK!!!
For those, desperate Dell Latitude D620 owners, or who esle, by the chance, owns this card - attached 100% working kext.
NB! Place this kext
to /System/Library/Extensions ANDto the "/System/Library/Extensions/IONetworkingFamily.kext/Contents/Plugins" folder
Do not forget to DELETE existing kext, and "chown/chmod/repare perms" of course!
I'm so happy, 'coz at workplace we don't have WiFi, and at last i can use MY OWN laptop instead this terrible monster, i have here...
(sorry for my english)
This kext only works on 32-bit (arch=i386).