I got a similar problem like the writer in this tread : http://forums.dlink.com/index.php?topic=2666.0
It started for about 2weeks ago.
My problem as I noticed it: All computers on LAN and WLAN side lossing their connection to the 655, after that they are getting new connection info (DHCP). This happens a few times a hour, 24-7.
On the Wan side : The router could som times reboot it self.
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My system
Internet -- DIR-655 : A3 and 1.20build3
-- WLAN -- 2 computers ( 1 Atheros 928x and 1 DWA-142)
-- LAN -- DNS-323 --- Gigabitswitch -- 2 computers (1 DGE-528T and 1 Realtek xxx )