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

See "Basic Troubleshooting: Make a new profile":

• https://support.mozilla.com/kb/Basic+Troubleshooting#w_8-make-a-new-profile

There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.

If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

See:

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

Unfortunately the profile manager can not be started either. I have also tried a clean install but the problem remains

Did you restore a file profiles.ini ?

• http://kb.mozillazine.org/profiles.ini_file

If you did then try to remove that file to make Firefox create a new default profile.

• https://support.mozilla.com/kb/Firefox+is+already+running+but+is+not+responding

• http://kb.mozillazine.org/Recovering_a_missing_profile
• http://kb.mozillazine.org/Profile_in_use