I'm having to clear cache constantly now in order to load pages.
Unless I clear my cache constantly, I get either an "invalid url" error or an "oops, no such page error"--sometimes an incomplete Web page.
URL of affected sites
many, some of which are new to me
Opaite Mbohovái (2)
Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes). See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems
If it does work in Safe-mode then disable all your extensions and then try to find which is causing it by enabling one at a time until the problem reappears. You can use "Disable all add-ons" on the Safe mode start window. You have to close and restart Firefox after each change via "File > Exit" (on Mac: "Firefox > Quit")
I think it was my Java plugin that was causing the problem. I now have another problem, but that may be ISP-related. I'm going to wait until my Internet connection gets right, then see what happens. Thanks.