You can check for sandbox security issues when Firefox has a problem to access local files

• https://wiki.mozilla.org/Security/Sandbox

You can set this pref to 2 or 1 on the about:config page to reduce the sandbox security level.

• security.sandbox.content.level = 1
• close and restart Firefox to make the change effective.

If '1' still doesn't have effect then try '0' to disable the sandbox.

If this didn't work then undo/reverse the change and reset the pref via the right-click context menu to the default value.

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

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

Original value was 4. Tried all 4 lower settings. Also tried whitelisting home directory and downloads directory tree.

No changes. Still can't update addons nor download any files.

Hi, please try a Refresh but Note that this does more than uninstalling and re-installing does. Normal uninstalling does not remove some preferences which may have become corrupt. Please Refresh but do this 1st: Delete your Cookies and Cache and TEST.

• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer
• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

then

• https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings

TEST....... If no issues then Extensions which need to be added back in 1 at a time and tested ..... Or it is your Profile : Make a new one and test ...:

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

If is your Profile :

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Note: Any customization will revert back to default, you will also need to reinstall Extensions.

As to Thunderbird I have no idea, sorry their forum is here : https://support.mozilla.org/en-US/products/thunderbird

Please let us know if this solved your issue or if need further assistance.

Can you open a file picker window otherwise (save file and open file) in case that is where it goes wrong?

cor-el

If I do a Save-As, I never get the box to specify where to save and what to call it.

Just clicking on a download link give me the following in the Browser Console but the download never starts:

GET https://clientupdates.dropboxstatic.com/dbx-releng/client/dropbox-lnx.x86-53.3.64.tar.gz [HTTP/1.1 200 OK 434ms]

Time to stop worrying about Firefox and Thunderbird. Just not worth the hassles anymore.

Pkshadow

Had already done everything you suggested and nothing made any difference. Firefox is dead.

The only reason I posted about Thunderbird was because I'm seeing the same error in the Console window that I'm seeing in Firefox. Figured there was probably some common code used in both.

Well, I finally figured out the problem with the help of an error trying to save a document with LibreOffice.

LibreOffice threw an error with them message "the object cannot be accessed due to insufficient user rights." Similar to what I was seeing with Firefox and Thunderbird.

Searching Google for that error produced a result that the LibreOffice path for Temporary Files was not set.

Sure enough, when I ran echo $TMP, there was nothing. Setting TMP="/tmp", logging out and back in corrected the problem in LibreOffice AND I can update addons and save files in Firefox and update addons and send email in Thunderbird.

Now to figure out why TMP is not set by default.

Thanks to all those who offered suggestions. This one had me totally stumped.