Are you using "Clear history when Firefox closes" to clear any data?

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings

Use "Firefox > Exit" (Windows: Firefox/File > Exit; Mac: Firefox > Quit Firefox; Linux: Firefox/File > Quit) to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

No, I am not. Firefox is set to its default settings (having never been changed) on all the computers. No other apps have been installed except for flash, silverlight, and MSE. All have new clean Win7 installs with all updates current.

All computers have brand new Samsung SSDs.

When I installed FF 28 from this same configuration, I did not see this issue.

When I installed FF 29 both with and without FF 28 being installed first, I see the problem.

I have sometimes got this issue and its normally caused by an addon of some type or a problem with the hardware mostly hard drives. Remove all addons and see if its still the same. Check hard drive for issues

Start Firefox in Safe Mode
While you are in safe mode;
Firefox Options > Advanced > General.
Look for and turn off Use Hardware Acceleration.
Poke around safe web sites and see if there is still a problem. Then restart.

I see the problem on at least 3 different computers, all set up from scratch with nothing more added to them than I stated earlier. They are all running Win 7 Pro 64 bit with 8GB memory. Two are Dell T1500 with i7 880 and 870 processors. One is HP 6200 Pro PC i5-2400 Quad Core 3.1GHz. All have Samsung EVO SSDs and where set up from scratch.

I also have a DELL i5-3470 QUAD CORE 3.60GHz 8GB memory Win 7 64 bit with the same SSD, set up the same way that does not have the problem.

And I also have many HP Compaq 6910p portables with 3GB memory, running Win 7 32 bit, and Samsung SSDs that do not have the problem.

All settings on everything are the factory defaults.

Did you already update to Firefox 29.0.1 (see Firefox menu button Help > About)?

Yes, I did.

See about:memory. Do you notice here any strange behavior?

I checked about:memory on one computer without the problem and one with the problem. I didn't see any obvious differences, but there was a lot of data to look through.

Both the computer with the problem and the one without reported "SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data" when I pressed "Read from Clipboard"

In case you are using "Clear history when Firefox closes" then try to disable this feature.

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [ ] "Clear history when Firefox closes"
• https://support.mozilla.org/kb/Clear+Recent+History

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

This problem is across many computers. Other than the few apps that were added (check my earlier comments), they are all pristine with new installs of win 7 and ff and haven't been used except for testing this problem. What would have caused all the profiles to be bad? Doesn't seem logical.

This problem has not occurred on any 32 bit version of Win 7 and it also hasn't occurred on one 64 bit version. I need to deploy these computers soon, I guess I will have to consider going back to IE 11.

Here is a thought;

LAST RESORT ! ! Reset Firefox


Pick one computer, reset that one only, and see if the problem remains.