I'm using Logitech Performance MX, coupled with Logitech SetPoint 6.50 (driver version 6.51, latest as of 22.3.2011). When Firefox is in focus some of the functions i have on my "special" mouse buttons are blocked. Blocked functions and buttons: Forward & back navigation button (go forward or back in websites, crucial for browsing) Right & left scroll with keystroke assingment functions (used for playlist manipulations) Application switcher with keystroke assingment (also for playlist manipulations) The scary thing is that when i change the application switcher from keystroke to play/pause it works perfectly. Also FF doesn't block the standard media buttons on my keyboard (they also go through SetPoint) What's worth mentioning, the keystrokes alone (if i press the combo on the keyboard) are not blocked, just the function from SetPoint itself is. Also the strangest thing is that it all worked in FireFox 3.6!