As of 3.4.7 there is a security check in place so as in the error message:
"
The file browser is disabled for one of the following reasons: 1. The user does not have sufficient privileges to access the file browser. 2. The file browser files do not have sufficient privileges to be executable. 3 This could be due to a security rule been applied by your htaccess file."
- You would recieve this message if all your files and folders permission for the editor are 777 and 666 and your joomla install requires them to be 755 and 644.
- You recieve this message,espically in J!1.7, if you are using and don't have sufficient privileges to use the file browser
- You would recieve this message if you have a htaccess rule blocking you from using the filebrowser.
Regards