firefox won't update
If there is an issue with update or permissions the better and safest way is to download and install firefox:
1. Download a copy of the latest firefox from http://www.mozilla.org/en-US/firefox/all.html
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.
see also: Installing Firefox on Mac
Please mark "Solved" the answer that really solve the problem, to help others with a similar problem.
har også det problem, jeg kan godt starte det og alt det der, men den går i selvsving når den skal undersøge kompatibiliteten.