As a strange little side-note for our problem with this... If I connect a console-cable to a "stranded" AP (I dont even have to log in - just start recieving log-messages), the AP will actually renew its DHCP IP on BVI1 - and then joins the controller. This made our debugging a bit hard to begin with as the error disappeared before getting any useful logs. We had to collect all logs via SSH/Telnet. We reproduced this behaviour several times on APs that had been stranded for several hours; every time we connect a console cable the same thing happens within a few seconds.
