Hi lexx2112.

Is your Ubuntu in English or a different language. There is a known bug in Firefox 58 that appeared on some Linux distributions placing language packs into Firefox ( https://bugzilla.mozilla.org/show_bug.cgi?id=1420775 ). The solution should be to go to .mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384} and remove all language packs you will find there.

Thanks for the quick response, I have checked and that directory is already empty unless you mean I need to do that after I have installed thre latest version?

Please check now, if the directory is still empty.

If it is empty and the error is still present, please also go to .mozilla/firefox/###.default/, where your profile is and rename extensions.json to extensions.json.bak.

Okay, I have checked all the above, I have installed Firefox again and I am getting this error:

XML Parsing Error: undefined entity Location: chrome://browser/content/browser.xul Line Number 381, Column 7: <menuitem id="context_duplicateTab" label="&duplicateTab.label;" </p>

Verify that you meet the System Requirements (GTK+ and GLib) for the current Firefox release.

• https://www.mozilla.org/en-US/firefox/system-requirements/
• https://www.mozilla.org/en-US/firefox/58.0.1/system-requirements/

You can create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/en-US/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 problems.

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

You can copy files like these with Firefox closed to the current profile folder to recover specific data.

• bookmarks and history: places.sqlite
• bookmark backups: compressed .jsonlz4 backups in the bookmarkbackups folder
• cookies.sqlite for the cookies
• formhistory.sqlite for saved form data
• logins.json and key3.db (decryption key) for Passwords saved in the Password Manager
• cert8.db and possibly cert_override.txt for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words you added to the spelling checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other Site Preferences
• sessionstore.jsonlz4 for open tabs and pinned tabs

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

What Firefox locale do you use?

cor-el said

What Firefox locale do you use?

en-GB

Does it mention what XML file or possible entity this is about?

Starting FF from the CLI gets a lot of these as it stats up...

(firefox:5500): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed

Okay, so I have just completed a full system upgrade and now I have got Firefox 58.0.1to load up properly.

Also all my cached passwords are now working!!

Thanks for your help,

Oh, and those square tabs, can they be changed, like back to the classic look rounded ones by any chance?

got it all sorted now...

https://github.com/wilfredwee/photon-australis