Modify file:

sudo nano /etc/network/interfaces

remove everything on wlan1

save and exit nano.

Modify file:

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

add to the bottom of the file

network={ 
     ssid="username" 
     psk="password" 
     proto=WPA 
     key_mgmt=WPA-PSK 
     pairwise=TKIP
     group=TKIP WEP104 WEP40
     auth_alg=OPEN 
}

save and exit nano.

In case of problems - or with minimal isntallation:

sudo wget http://dl.dropbox.com/u/80256631/install-rtl8188cus-latest.sh -O /boot/install-rtl8188cus-latest.sh
sudo /boot/install-rtl8188cus-latest.sh