I'm trying to accomplish locked preferences for Firefox as well. I've found various web sites detailing how to do this, but no matter what I try, I'm getting "Configuration Error: Failed to read the configuration file. Please contact your system administrator."
I have a perl script which is "encrypting" the file with rot13, and I'm placing it in /Applications/Firefox.app/Contents/MacOS/grepprefs/
Any idea where I'm going wrong?
Thanks.