Well, after the Thanksgiving holiday break, I'm ready to tackle this thing again. I was able to try an ethernet connection during the holiday (both on my home network and at the hotel where I am staying otherwise) and it didn't have any effect. I'm not sure exactly when this happened, but now IE won't pull up Google sites, only Firefox will. And I can't get any other sites on Firefox but Google sites, but it doesn't always hold true. I can go to the Google search page and click on most of the links (images, shopping, etc.), but some of them I can't pull up. I can go to the "videos" page and see the thumbnails but when I click on the link, the page comes up but the video display is just B/W static like an old B/W TV. Sometimes the issue will clear up on its own after a few to several minutes, and other times I have to reboot. It doesn't seem to make any difference whether I clear the DNS cache, do the IP reset, etc. as long as I do a full shutdown and restart. Sometimes when I hibernate it will reset everything and sometimes it doesn't. Sometimes I can disable and restart the wireless adapter and it will fix the problem and sometimes it won't. I thought for a while it might be the result of extended internet use, but I've had some instances lately where the problem flared up just a few minutes after startup. It just doesn't seem like there's any rhyme or reason to it!
By the way, I tried setting the DNS servers manually as suggested. It didn't help.