Setup: tmux 1.8 running on Ubuntu 12.04 connecting from Windows with Putty. tmux has mouse mode on.
Steps to reproduce: Select the putty window as active, but use the mouse off the window (i.e in another window) Typically this happens when I am scrolling in another application on another monitor but forgot to switch the mouse focus.Also, this only happens if the putty window is large or maximized.
Issue: Junk commands get dumped into tmux (e.g 7#, H#, 7a etc.) If I scroll off window with only PuTTY (no tmux) the screen scrolls as expected.
Update: I have determined that this happens if my putty window is has >= 224 columns