I have a 4318 in this laptop, and have had no luck at all with it using the bcm43xx driver. I don't think I will be buying any more Broadcom products.
According to the devices section
http://bcm43xx.berlios.de/?go=devices
The 4318 is unstable at present, however I have absolutely no problem with using ndiswrapper.
Install ndisgtk if you don't want to muck about in the shell, and let it do it for you. Remember to add the line:
blacklist bcm43xx
to /etc/modprobe.d/blacklist
I use wifi-radar for managing the connections. It just works.