What is your computer system and Firefox?

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

I'm running mac osx 10.7.5. Firefox won't work long enough for me to get in and see what version it is, but I checked earlier today and it said it was up to date, so I have the newest version that will run on osx 10.7.5.

I've already tried opening in safe mode and it still won't load anything.

How did you remove the history and did you only clear the browsing history or also other items like cookies and cache?

Create a new profile to test 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 problems.

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

I deleted history, cache, and cookies for the previous hour by shift command delete.

The new profile worked. Is it better not to transfer files from the old profile? Is there a way to know which files were corrupted?

You can try to transfer one file at the time, but if you cleared the browsing history then it is likely a problem with places.sqlite (bookmarks and history).

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

• bookmark backups: JSON backups in the bookmarkbackups folder
• SQLite files like cookies.sqlite (cookies) and formhistory.sqlite (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.js for open tabs and pinned tabs and tab groups

See also:

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

Oh, wait. I was a bit too hasty and deleted the old profile. I did not delete the files. Is there a way to still get bookmarks back from that even though I can't open the old profile from the profile manager?

If the bookmarks are the problem, then I won't bother transferring anything - that's all I would really want to save if I could. Thanks for the help!

If you used the Profile Manager to delete the profile from the Profile Manager window, but left the files then the profile folder is still on the hard drive.

You can use this button to go to the current Firefox profile folder:

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

Go up one level to find the other profile folder. It shouldn't be a problem to restore the bookmarks from a JSON backup in the bookmarkbackups folder.

• https://support.mozilla.org/kb/restore-bookmarks-from-backup-or-move-them