I have a D-Link DIR-615 using it only as an AP no DHCP from the router.  I have the security setup as Auto (WPA or WPA2)-PSK 
Firmware: 3.10N
Hardware:C1 
At least 3 times a week I get limited to no connectivity from 3 different devices, 2 laptops and a smartphone.  
I have checked the logs and i keep seeing Wireless system with Mac address 00:25:xx:xx:xx:xx disassociate reason 8, as well as Wireless system with Mac address 00:23:xx:xx:xx:xx deauthenticate reason 3.  From what I found both those codes mean : Operating System moved the client to another access point using non-aggressive load balancing  and  The access point went offline, deauthenticating the client.    I am thinking that the access point may be going offline.  the question is how do I correct this?