I'm also seeing a mouse problem. It involves the combination
shift-leftbutton-rightbutton (intended to emulate shift-middlebutton) after
I've started XWin with -emulate3buttons. I use a 2-button mouse with a scroll
wheel that can be pressed to serve as a third button. But I find it hard to
press the scroll wheel without turning it, so I prefer to use -emulate3buttons.
The shift-left-right combination used to be seen by emacs as shift-middle, but
now emacs doesn't seem to see it at all. Moreover, after I press it once,
either in emacs or elsewhere, both emacs and xterm stop responding to some
other mouse events.
To reproduce (without emacs):
1. Start the X server with
startxwin -- -emulate3buttons
2. Press shift-left-right in an xterm window, using a mouse of the type I
described.
3. Move the mouse over the titlebar of the xterm window. The menu items don't
get highlighted, and left-clicking on them has no effect.
The problem disappears if I remove the -emulate3buttons option; but that's not
a good solution for me since I actually want to emulate 3 buttons.