Since I updated to 2.74, sometimes the mouse wheel scrubs the timeline rather than zooming. I guess I've hit some key by mistake, but I haven't been able to find out which one. When this happens, scrolling scrubs the timeline no matter which part of the UI I'm in, i.e. it won't let me scroll up and down in the panels either.
Update: I have several virtual desktops, and after posting this, when I went back to the desktop where Blender is, it had reset the mouse function to what I'm used to. Seems strange. Is this a bug that I should report, or is it some feature that I haven't been able to wrap my head around?