Try to toggle gfx.xrender.enabled on the about:config page.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

Could you check this thread started by another Linux user and see whether the workaround there helps on your system:

how do I stop firefox ffrom blocking out urls

The workaround there was:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste gfx and pause while the list is filtered

(3) Double-click the gfx.xrender.enabled preference to switch its value from true to false

This takes effect after the next time you exit and start up Firefox again.

Does that work for you?

Thank you both!

I'm pleased that this info worked for some but it screwed up my Toshiba Satellite SL10 (2005 vintage) running Linux Lite - the ENTIRE firefox window is blaNk! I can't even get to about:config to reverse the Boolean. Neither can I find any file in the xxxxxxxx.default folder that might hold this value and so change it.

What can I do now? (he wailed)

Hi pofadda, most changes made in about:config are saved in the prefs.js file in your active profile folder. Please see this article for how to locate that folder. After exiting/quitting Firefox, you can open the prefs.js file in a text editor and delete that line.

Profiles - Where Firefox stores your bookmarks, passwords and other user data