Until last week, my Logitech trackball M570 worked without problem. Recently, however, things have changed. If I stop and restart Firefox, most things work right other than forward/back buttons. If I open a new window from a link in an existing open window, nothing works including scrolling. I then have to shut down and restart Firefox again. I thought maybe my trackball was bad so I purchased a new one. Installed and the problem still exists. So it is not my trackball. Contacted Logitech and followed all of their recommendations and that didn't help. It only seems to happen with Firefox. Works on Internet Explorer fine. Running current version of Win 7 Home Premium. I can't remember if this problem started after the last Firefox update or not.