Have you tried a reboot of the computer?

Do you see that (hidden) window if you minimize the Firefox browser window?

At least ten times.

Sorry. This works differently from how it looks.

Thanks for the replies.

I have rebooted at least ten times since this started happening.

And no, there appears to be no way to actually SEE the dialog box, but for a while, if I hovered my mouse in the right place, it would change to the two-sided "resize" arrow that you see at the edge of an active window. Also, as I said, there is evidence that it is there, because if I click on something outside of FF, and then click within FF, and then hit enter, the file saves, as long as there is no name conflict. Then, I can go back to browsing. But if there is a name conflict, it seems there is nothing I can do but close FF from the task manager, and restart.

Does that window show in the Alt+Tab list?

Can you open a system menu via Alt+Space if you try to select that window?

Try to check for problems with the localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

Hi Cor-el.

It does NOT show up in Alt+tab.

I don't seem to be able to select the dialog box, and if just the FF window is selected, alt+space does nothing, if this problem is happening at the time.

I deleted localstore.rdf with no change.

Interestingly, the save as dialog box has defined edges, which change my cursor to the double sided arrow, and I expanded it pretty big, but it's still invisible! Everything else has stayed the same.

Has everyone given up on this?

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode

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

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 some files from an existing profile to the new profile, but be careful not to copy corrupted files.

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

Do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 19.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Cor-el, thanks so much for all the help! I'll do my best to follow your instructions and report back.

So...

I tried safe mode, and FF went completely black. I did it twice, and I'm pretty sure I restarted windows first. This told me something was seriously wrong, so I skipped the profile thing, and went straight to the uninstall and then installed a new copy. I followed your directions closely, and...

it worked.

Everything seems fine, now. I had thought of this, of course, but Cor-el's instructions on just how to do the uninstall made me confident I could do it and get what I needed done, without screwing anything up in the process.

Thanks again!