Mouse buttons stopped working in IDEA - help?!

On my laptop I have build 3425 (no internet connection on it in the office at the moment so can't update) installed and it had been quite happily working until the other day when all at once all mouse activity in the idea window no longer works. Can't click on any menu, in the editor, use the mouse wheel or anything. Butons still hilight when the cursor is over them but there is no response to clicking.

I had the zip version of 3425 on the hard drive, so removed all but the jre and reinstalled also removing my .intellijidea50 directory in case something had got corrupted - no joy. I even changed the mouse. No change.

IDEA seems to be the only application affected - other java apps have no problems.

Any ideas/suggestions as I'm getting rather frustrated! (though I am getting good with the keyboard shortcuts at least!)