Very odd. Since you have so many extensions, I wonder whether you would test with those disabled. A standard diagnostic for interference by add-ons is to try Firefox's Safe Mode.

First, I recommend backing up your Firefox settings in case something goes wrong. See Back up and restore information in Firefox profiles. (You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder.)

Next, restart Firefox in Firefox's Safe Mode (Diagnose Firefox issues using Troubleshoot Mode) using

Help > Restart with Add-ons Disabled

In the Safe Mode dialog, click "Start in Safe Mode." Does that still have the blank tabs?

Note that Safe Mode makes other possibly relevant changes in addition to disabling extensions, and you can try those manually if you like before trying to figure out which extension it might be:

(1) Disable hardware graphics acceleration

Your "More system details" shows that this already is disabled for your graphics adapter, so you can skip this.

You usually need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

orange Firefox button or classic Tools menu > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

(2) Clear toolbar customizations

(i) Open your personal settings (AKA Firefox profile) folder

Help > Troubleshooting Information > "Show Folder" button

(ii) Switch back to Firefox and exit the program (e.g., Firefox > Exit or File > Exit)

(iii) Wait a few moments for Firefox to finish updating files in your settings folder, then rename localstore.rdf to something else, like localstore-bad.rdf or localstore.old.

(iv) You can restart Firefox now. If that didn't help and you want your customizations back, you can delete the newly created localstore.rdf and rename the old one back.

Note that the value of 0 isn't a valid value for the permissions.default.image pref.

• http://kb.mozillazine.org/permissions.default.image

I have not had the opportunity to try any of your fixes, but with the upgrade to 15.0.1, I have not had this problem anymore. Thanks anyway for your help.