= Why a Blank Profile? =

Very often, when experiencing a problem with Firefox extension, some particular settings or other extensions in your profile may be interfering.
It is an extremely powerful debugging tool to try to reproduce the problem in a blank profile, and see if it still happens.
If it does, it's a problem with just that extension.
If it doesn't, the problem is to locate the conflict.

= Testing For a Conflict =

To create a blank [http://www.mozilla.org/support/firefox/profile profile], follow these instructions.
You can also follow [http://www.mozilla.org/support/firefox/profile#new these instructions] from Mozilla, with screenshots.
(Note, substitute Thunderbird for Firefox anywhere below, for extensions for that program.)

 1. Close any running Firefox windows.
 2. Start Firefox with the `-profilemanager` command line argument.
    * For Windows, click `Start`, `Run...` and type: `firefox -profilemanager`, then click OK.
    * For linux and mac, just type `./firefox -profilemanager` (from within the directory Firefox is installed in, varies by distribution.)
 3. Select `Create Profile...`, click `Next`, and in the box that comes up type a name, like "test".  Click Finish.
 4. Select the profile you just created, and select `Start Firefox`.

After testing is complete, repeat step two, but select the original (probably "default") profile to switch back.
This way, you don't have to install/uninstall or disable all of your existing extensions!

= Finding the Conflict =

If the blank profile ''does'' resolve the problem, it is usually best to start installing all of your regular extensions, one at a time.
After each one, check if the problem comes back.
When it does, the last extension installed is the culprit.