Yesterday, I upgraded my Mac to Mac OS X 10.9 (Mavericks), and since then I couldn’t open the “Terminal,” each time I open a session, the following error is shown:

> 
> [Could not create a new process and open a pseudo-tty.]
> 
> 
> [Command not found: tmux]
> 
> 
> 

I don’t know what's causing this issue and a fresh restart and killing the relevant processes on activity monitor doesn’t help. Any thoughts?