Hour and a half fiddling to get wpa_supplicant working on my Lenovo ideapad. It just wouldn't go. Set up the link, but then I was having to run dhclient manually. Well the answer was hidden on someone else's blog - the line in rc.conf needs to be:

ifconfig_wlan0="WPA SYNCDHCP"

Instead of:

ifconfig_wlan0="WPA DHCP"

Must be to do with using the ndis module, it needs the pause to connect. Sadly, this doesn't seem to be documented in either the wpa_supplicant or dhclient manpages :-(