Hi,

Please also try deleting any parent.lock files inside any of the Firefox Profile Folder, if present.

Firefox Profile Folder & Files

It is a problem with the Firefox program folder (C:\Program Files\Mozilla Firefox\), so no need to check the profile folder.

If there are problems with updating then best is to download the full version and uninstall the currently installed version and delete the Firefox program folder to remove any leftover files.

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

• Firefox 10.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible.

• Do NOT remove personal data when you uninstall the current version or you lose your bookmarks and other data because all profile folders will be removed.

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 elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if 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

Thanks for the suggestions, guys. I have been waiting for the next update to see if it was fixed..

I have tired the full uninstall/reinstall route suggested by cor-el and checked that there are no parent.lock files left over when I exit Firefox.

Unfortunately, I still have the problem with the latest (11.0) upgrade.

Nothing seems to work :(

Maybe I'll have to bite the bullet and zap the whole install and profiles and start from scratch...

Has Firefox been used from other accounts on the same PC??

I've also suffered this problem on win 7 64-bit, for both firefox and thunderbird. it happened with 8, 9, and 10. I've been down the uninstall / reinstall path, but it always returns as soon as an update is released.

can't this be fixed? Is there a bug logged against it?

No, no one else has used this laptop at all. Just me. I have re-run the various suggestions and still have the problem - with both Firefox and Thunderbird. It seems that there must be something at a lower level that affects both applications. I do have admin rights on my pc but it is a corporate build so it is possible there is some deep policy that makes this happen? By the way, I don't have the problem on my personal laptop, also running Win 7 64 bit, so, unsurprisingly, it's not a problem with the OS