I'm having this problem now (in all Emacs versions, on MS Windows): Clicking the mouse wheel in Win32 Emacs causes the little AutoScoll symbol to appear instead of pasting. If you click the mouse wheel again, the AutoScroll disappears and the pasting occurs. If you change the wheel click to anything other than the default, then pasting in Win32 Emacs doesn't work at all (IIRC). http://www.cygwin.com/ml/cygwin-xfree/2003-07/msg00252.html
This just started happening, after I updated my mouse driver. I tried rolling back the driver - didn't help. I downloaded a new driver - didn't help. I see the problem even with different (Intellimouse) mice. Symptom: When I click the wheel button (`mouse-2' for Emacs), the first click is intercepted by Windows and displays the autoscroll pointer. I must click it again to get Windows to pass the mouse event to Emacs. E.g., if I do `C-h k' and then click the wheel button, the Windows autoscroll pointer appears and Windows initiates autoscrolling. If I then click it again, Emacs receives the `down-mouse-2' event and I see the output from `describe-key'. As I say, this is a new problem for me, and I can't seem to turn it off. It always just worked before. I see the same problem in all Emacs versions, and -Q or not. In the mouse properties box, I have the Wheel Button set to its default value of AutoScroll. I tried setting it to None, but then no event is sent to Emacs at all. I tried setting it to Paste, but that sends a `C-v' to Emacs. I tried setting it to Redo, and that sends `C-y' to Emacs, but that's not what I want (and, besides, I don't want the middle mouse button to be Redo in other apps). I want to be able to bind `down-mouse-2' to a particular command, and have Emacs actually receive `down-mouse-2' and `mouse-2' events, not `C-y'. Help appreciated.