One thing you may want to check is to make sure that the "Disable Gateway Smart Packet Detection" box is checked.
When I was using the SMCD3G-CCR, I found that when that box was unchecked, the router would sometimes lose its html interface (and/or just lock up period). If you have had reason to have a Comcast CSR poke around in your SMCD3G lately, they may have unchecked that box (that happened to me several times).--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.