It sounds kind of like this issue:http://support.intel.com/support/wireless/wlan/sb/cs-022427.htm

I am running 4.0.179.8 and my APs do this too. I am running 1030 APs. They don't do it every hour but it is probably at least once every day or two. When this happens I get a message for every AP Operation State Down: ... Cause = Unknown and short...

We restrict dial in access by phone number but we do it through our phone system instead of the network equipment. Do you have the capability to do this on your phone system?

I ran into this problem yesterday. We just recently went live with a 4402. In my case I was seeing that error message generated by a handful of machines with Intel 3945ABG wireless cards. The machines were running with an old driver version and wh...