Just reporting a problem I've hit... I wanted to play in a window on my bigger attached monitor rather than my laptop's built-in screen and found that when I switched out of full screen and moved the Nex window over to my external monitor, the cursor broke.
Steps to reproduce: unzip 2.5, open game, open settings, open video, turn off "Full Screen", switch to another program (command-tab), move Nexuiz window, try to play. Curiously, you can move it a few pixels and it will still work. If you move 100 or so however, even if the main menu sections are still mostly lined up pixel-wise with where they were, nothing works. Nothing odd in the log.
I wanted to eliminate my very mucked-around-with machine as the cause so in addition to that machine (a fully up-to-date MacBook Pro), I tested with a newly unboxed MacBook using the just the internal trackpad and the internal LCD, and an iMac with a Kensington mouse and their MouseWorks drivers. Untested on other OSes.