Description of problem:
Firefox provides a method of locking preferences via the "general.config.filename".  However Fedora's build of firefox fails to find the configuration file.  It will read the "general.config.filename" setting and is either looking in the wrong place for the config file or fails to read it altogether.

Version-Release number of selected component (if applicable):
This is with version 3.0.2-1

How reproducible:
ALWAYS

Steps to Reproduce:
1. touch /usr/lib64/firefox-3.0.2/defaults/preferences/loadcustom.js
echo "// tell firefox to load customized config file" >> /usr/lib64/firefox-3.0.2/defaults/preferences/loadcustom.js
echo "pref("general.config.obscure_value", 0);" >> /usr/lib64/firefox-3.0.2/defaults/preferences/loadcustom.js
echo "pref("general.config.filename", "mozilla.cfg");" >> /usr/lib64/firefox-3.0.2/defaults/preferences/loadcustom.js

2. touch /usr/lib64/firefox-3.0.2/mozilla.cfg
echo "// lock browser to auto-detect proxy settings" >> /usr/lib64/firefox-3.0.2/mozilla.cfg
echo "lockPref("network.proxy.type", 4);"

3. Start-up Firefox.  
  

Actual results:
You'll receive the following pop-up message
"Failed to read the configuration file. Please contact your system administrator."  click on OK and firefox closes.

Expected results:
Firefox should open to the user's configured start page.  *AND* Firefox should be configure to auto-detect proxy settings *AND* the user _can't_ change that setting.

Additional info:
I confirmed this is a bug with Fedora's build by trying the binary from mozilla.org

http://support.mozilla.com/tiki-view_forum_thread.php?forumId=1&comments_parentId=43099

https://developer.mozilla.org/En/Automatic_Mozilla_Configurator:Locked_config_settings