D-Link DIR-655 :: Wireless Internet Occasionally Drops Out?

I have a new DIR-655: H/W Ver. B1; F/W Ver. 2.00 NA? It is solid as a rock to my wired computers, but the Internet connection (not the wireless signal) to my wireless devices (laptops and smart phones) occasionally drops out for several minutes, many times each day. It is not necessary to reset my router to reconnect; after a while wireless Internet returns on its own. I upgraded from another D-Link router and never had this problem. In my judgment the problem appears to be the router. why the wireless Internet connection might disappear and then reestablish itself?I used an app on my smart phone to select Channel 11. No neighbors have routers close to this channel. My cordless phones are DECT (1.9 MHz). My microwave oven does not cause this dropout.

The DIR-655 wireless settings are pretty standard:

 - WPA personal security mode
 - WPA mode is Auto (WPA or WPA2)
 - Cipher is TKIP and AES
 - Group key update interval is 3600 seconds
 - 802.11 mode is mixed n and g

When this wireless Internet connection dropout occurs, the router's signal strength does not decrease; the Internet connection just disappears. Time after time I have confirmed that the integrity of the Internet connection remains solid on my wired computers and disappears only from my laptops and smart phones.I have checked the wireless spectrum when the wireless Internet connection disappears. There is no other signal, e.g., no neighbor's router on my channel (11), and the strength remains at 5 bars.