I also updated to version 3.6.8

Same problem after update to v 3.6.8

Same problem with 3.6.10

• "Clear the Cache": Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"
• "Remove the Cookies" from sites that cause problems: Tools > Options > Privacy > Cookies: "Show Cookies"

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

Also make sure that you do not zoom the page.
See:

• http://kb.mozillazine.org/Zoom_text_of_web_pages

I tried clearing the cache (although the path to clear the cache is different on a Mac) but it did not help. The login page still gets stuck and never completes the log in. Looking at the address line, the last eight or ten letters of the address change repeatedly, but the page never continues past that point.

Did you clear the cookies as well?

• "Remove the Cookies" from sites that cause problems: Firefox > Preferences > Privacy > Cookies: "Show Cookies"

• http://kb.mozillazine.org/Error_loading_websites - "Error_loading_some_websites"

I had this same problem too. It was just Yahoo that wouldn't load right, and just on firefox. How many people are running Ad Block? I fixed the problem on mine by going to Tools > AdBlock Plus Preferences. Then I removed all the custom filters. (I didn't want to go through them all to see which one would fix it.) Now my page loads just like it's supposed to. Hopefully this will help somebody else.