I spent some time trying to make the wifi router run as a client, but to no avail. The only thing I saw in dmesg ifter enabling wifi was
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
It seems there's a number of people with similar problem.
Finally I located the fault in the device's default configuration:
config wifi-device radio0
option type mac80211
# option channel 11
option hwmode 11ng
There seems to be a problem with the 802.11n mode, after changing the setting to just '11g' the client mode works as a charm.