That does not seem legitimate. When a new Firefox update is available you get a pop-up box similar to the attached image, or for a minor update it will say "An update to Firefox is available" and give the Firefox version number. You are currently using the latest version of Firefox 3.6 so you should not get that pop-up. You can get a bar across the top with an Allow button if a site is trying to install an extension. You will not get a message from Firefox stating "Critical Software updates available, please allow", so I would treat this as something malicious. To ensure the computer is not infected, try running several malware scanners. It is best to run several as each will pick up things that the others miss. Some scanners you can try are: * Malwarebytes - http://www.malwarebytes.org/mbam.php * SuperAntiSpyware - http://www.superantispyware.com * Ad-Aware - http://www.lavasoft.com/products/ad_aware_free.php * Windows Defender - http://www.microsoft.com/windows/products/winfamily/defender/default.mspx * Spybot S&D - http://www.safer-networking.org/en/home/index.html

Thanks for the input Tony. I ran all 5 scanners, still have the same trouble. I'm thinking of upgrading to Firefox 4 and see if the problem persists.