Compaq Mini 730OE Broadcom BCM4312 Wireless flakyness

Symptoms: Can't connect... 4-way handshake timeout. deauthenticated by Reason: 15.

First of all you need the b43 firmware:

apt-get install firmware-b43-lpphy-installer

Then put this in /etc/modprobe.d/b43.conf:

options b43 pio=1 qos=0