This stumped us too.
It was a rare find and we were happy IT HAPPENED TO US because we found an elusive issue that strikes some folk. Ready? The router arrived and was set to EU WiFi channels. This worked for most but not all machines as the machine that didn't work were set to look for NA channels.
More at http://en.wikipedia.org/wiki/List_of_WLAN_channels
Notice channels 12, 13 and 14?