How to stop "...help improve Mozilla FF" popup??

[ca1977a]

Hi,
How do I switch off the popup saying "Would you like to help improve Mozilla Firefox etc" every time I open a new Firefox window? I'm trying to run automated tests of our web application (using Selenium) but now they're getting blocked by this message.
This is Firefox 8, it was working fine after I upgraded it yesterday but started doing it at some point this morning. I have tried answering both yes and no to the popup, and have also unchecked Submit Performance Data in Options, as was advised on another forum.
Any help much appreciated!
- Chris

[Vitesse]

Sounds like you may somehow have got onto the beta channel. Have a look in Help > About Firefox and see what it says there.

[KWierso]

Can you set the following pref to '2': toolkit.telemetry.prompted and see if that works?