Only US wireless channels enabled by default
I don't know from wich kernel version this started but it affects wireless drivers wich use the new mac80211 system.
The mac80211 system defaults to the US regulatory domain for wireless, so wireless networks on channels forbidden by US regulations but permitted by European or Japanese regulations will not work out of the box. This affects IEEE 802.11b/g channels 12 (Europe and Japan), 13 (Europe and Japan), and 14 (Japan only), as well as all 802.11a channels.
To work around this, create a file named cfg80211 in the /etc/modprobe.d directory.
Put the following line in it to use European wireless channels:
options cfg80211 ieee80211_regdom=EU
Put the following line in it to use Japanese wireless channels:
options cfg80211 ieee80211_regdom=JP