Mouse loses click ability (winxp host, ubuntu guest)

I've got an odd problem here. While running ubuntu, my mouse will suddenly lose the ability to 'click'. Movement is still working fine. Restarting X via ctrl + alt + backspace *sometimes* brings it back, but not always. Curiously enough, the mouse1 button always seems to work on the login screen when I restart X, but not once the desktop fully loads.

More curiously, while I'm experiencing this issue, I can switch to a terminal (via contrl + alt + F4 or something) and cat /dev/input/mice, and my clicks *are* being passed to the guest OS.

So this seems to actually be a bug somewhere in either X or Gnome, not parallels. Has anyone else experienced this? Any solutions/work arounds?