hello paul, can you update your system to os x 10.6.8 first? afterwards try to load the full firefox offline installer for your language and system from https://www.mozilla.org/firefox/all/

Actually, if you have compatible Hardware (basically a computer made in 2008 or later) you should update to Mac 10.9 for Free... http://www.apple.com/osx/ as support for Mac 10.6 will be going away (plus it's horribly insecure and slow).

After doing that, go to www.getfirefox.com and download and install Firefox 25

Hello desmond2, if you have problem with update firefox the better way is to download and install the new version, as correct said philipp in his above reply, and yes, you must delete the older version of Firefox and then install the new/latest one.

1. Download a copy of the latest firefox from philipp's reply link

2. Trash the current Firefox application to do a clean install.

3. Install the version that you have downloaded.

Do not select to remove your personal data, your profile data is stored elsewhere in the Firefox Profile Folder, so you won't lose your bookmarks or other personal data.

after the upgrade see :Common questions after upgrading from Firefox 3.6

thank you