I'm developping a web application in silverlight. I've never having a problem with silverlight or firefox since 1years. But 2 days ago i download FF 3.6.4 and then i can't debug my web app anymore ! I've spend 4hours to reset my setting in visual studio, try older project etc. Then i try to put IE as standard web browser, then it works with IE ! The same for chrome ! Firefox is loved by developpers, if they can not debug their application, they will move to another browser, even they got dozen awesome plugin :( == This happened == Every time Firefox opened == I start debuging my web application (silverlight)