Can you try the following?
Set the WiFi mode on the 657 from Mixed all mode to Single mode G, 20Mhz Only, WPA and TPIK only.
You'll need to reconnect the printers WiFi and the iphone to the routers WiFi SSID again.
Then test with Mixed G and N only, 20Mhz, WPA2 and AES Only.
Keep us posted.
I probably wont be able to test this as I don't have a WiFi printer. Only USB and LAN supporting printer.
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