Apparently, that weird thing with the d20SRD site was somehow connected to Google. When I clicked on a link to a d20srd.org page from a Google search page, that rendered the page inaccessible and somehow invisible to my system. I discovered this when it happened on my desktop machine, too -- though it didn't happen on Quel's.
The Fix? Firefox > Tools > Clear Private Data, which purges Browsing History, Download History, Saved Forms and Search History, the Cache, any and all Cookies, Saved Passwords, and Authenticated Sessions. I just checked the boxes on ALL of those, and cleard the whole shebang.
It worked on both machines -- and now Google will send me to d20srd pages with no problem.
So, I have no idea WTF this was all about.
It could be that taral's suggestion that my profile was somehow borked was the answer -- if so, then I found the one easy way to fix it!
Thanks for the feedback and suggestions, gang.