Thanks, Animal. I called Comcast and got to 2d Level Security and sorted it out.
You are correct -- static IPs are assigned by Comcast since they charge for the privilege. They didn't tell me I needed a Comcast-supplied moderm or router, but since they publish the list of compatible devices and mine were on them, I don't think that would have been an issue. They were more miffed that I had the temerity to even try to use a fixed IP of my choosing, though they understood it was for testing only.
They told me that I was not the only Michigan user getting plugged into Georgia. They had been updating their local server and had shunted users down there until they completed the work. I re-enabled dynamic IP assignment, reloaded all pages, and even without rebooting either modem or router was able to re-establish local connectivity. So their upgrade had finished, it seems, and I was able to restore my connectivity.
Though I must report it was not an immediate thing. It took time for my rig to find a DHCP server, though Skype connected without an issue, silently, and longer still for pages to actually appear under their proper URLs. Nonetheless it happened, my latency is no longer 45ms, and I have no further problems with my browser crashing -- with the sole exception of the Comcast TV listings page, which crashed me like a cheap Renault.
Thanks for your help, Animal. I appreciate the advice and suggestions. My problem is resolved, and I camp happily now.