I'm running VIM in tmux,
When I'm try to select a range of texts in VIM, the mouse kept resetting its position, thus I can only select one line (the last line where mouse occurs).
Does anyone know how to solve this?
There are two settings that you need to configure for this to work.
In your .vimrc add:
set ttymouse=xterm2
set mouse=a
In your .tmux.conf add:
set -g mouse on
You will then be able to use the mouse to select blocks of text, resize splitted windows, ...
set -g mouse on
                
                The answer by @jasonwryan won't work as of tmux 2.1 since the several mouse options were merged into one configuration called mouse.
The new approach is:
In your .vimrc add:
set ttymouse=xterm2
set mouse=a
In your tmux.conf add:
set -g mouse on