Hi Fgl30,
I've not heard of the specific problem your describing, can you nail down some details for us? When you said, you have seen it on wireless too, what OS were you running on that PC? Please give DIR-655 hardware and Firmware currently running. I am really tyring to see if it is OS & Firmware specific/combination there of.
I would request you to change the Lease time on the DHCP offers, then, comment back if problem is only occurring with that loss of IP (due to DHCP Lease expiration) and then your sporadically not getting and Offer/IP back. This is not a wide spread epidemic with the DIR-655; just specific to your network at this time. Also, if you have upgraded your firmware and had not noticed this problem before, I would have you clear the router of any previous configuration (Reset to Factory Defaults) see if the problem still exists. If you have the time to do so, please let us know the outcome?