Download latest Firefox version using one of these links:

• http://www.mozilla.com/en-US/firefox/new/
• http://www.mozilla.com/en-US/firefox/central/
• http://www.mozilla.com/en-US/firefox/fx/
• http://www.mozilla.com/en-US/firefox/all.html

Uninstall your current Firefox

• https://support.mozilla.com/en-US/kb/Uninstalling%20Firefox
• DO NOT SELECT TO REMOVE USER DATA AND SETTINGS

Install Firefox using the downloaded & saved Firefox installer file

• https://support.mozilla.com/en-US/kb/Installing%20Firefox%20on%20Windows

Check and tell if its working.

tried that twice. if I could get an earlier version I would install and try. First tho I will rollback to a restore point.

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

-> Basic Troubleshooting: Make a New Profile

• https://support.mozilla.com/en-US/kb/Basic%20Troubleshooting#w_8-make-a-new-profile

-> If that New Profile works then you can recover your Bookmarks and Passwords from the Old Profile.

-> Recovering important data from an old profile

• https://support.mozilla.com/en-US/kb/Recovering%20important%20data%20from%20an%20old%20profile

Check and tell if its working.

This won't help the OP, but FWIW I simply reinstalled 6.0.2 (without doing the uninstall) and all appears to be well.

Do you have ZoneAlarm Extreme?

• [/questions/869812]
• [/questions/869951]

tried to run but the same problem occurs - I cannot get past the error to be able to change the profile.

tried that too....

yes. I shut down zonealarm and reinstalled but the same error occurs.

XULRunner error after an update

• http://kb.mozillazine.org/Browser_will_not_start_up#XULRunner_error_after_an_update

Check and tell if its working.

same old..... removed firefox as completely as I could see from directories and registry. shut down zonealarm. fresh reinstall. still no joy.

Did you make sure that all files in the Firefox program folder (C:\Program Files\Mozilla Firefox\) are removed and that folder as well?

You can try to boot Windows in Safe mode (press F8 on the boot screen) to see if that allows to install Firefox.

You can also try a custom install in a different directory like "C:\Program Files\Mozilla Firefox6\"

• https://support.mozilla.com/kb/Custom+installation+of+Firefox+on+Windows

hhmmm. I created a new directory, and installed ok. checking all the instances of firefox and version references in files across the pc will take a while. but I'll see if I can find the offending snippet.

Installing using the custom option and designating a new directory worked for me also. Thanks for the suggestion.

Glad to hear it