Comment 16 for bug 1545302

/etc/network/interfaces:
--------------------------------------
auto lo
allow-hotplug wlan1

iface lo inet loopback

iface wlan1 inet manual
    wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf

iface default inet dhcp

/etc/wpa-supplicant/wpa-supplicant.conf
-----------------------------------------------------------
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    ssid="Sooty"
    key_mgmt=WPA-PSK
    psk="secret"
    priority=5
}

Basically the same as yours. It's worth confirming the symptoms: for me this setup was working fine until a recent apt-get upgrade. After that, wireless appeared to come up but no address was assigned over DHCP. I could get one by manually running "dhclient wlan1". It was apparent looking at the logs that dhclient was not being run after the wireless connection came up, and the PPA from Dariusz has dhclient running again.