This problem just began this morning. Whenever I move my mouse over the tabs list (I've got lots open at the moment) it scrolls constantly to the right. I can rotate the scroll wheel to move it back to the left, but then it automatically begins to run right again. Additionally, this morning when I clicked shift while trying to type Firefox kept forcing me to the previous page. I chased down the solution to the shift problem (by disabling the shift value to 0 for mousewheel.with_shift.action), and did the same with control, alt, and default. This hasn't solved the odd scrolling problem. The keyboard is only a few months old and working fine for every other application. Chrome does not exhibit this problem.