Well, try changing to your planeshift install directory, and try running ./pssetup, just in case you don't know of it. I would try setting the game to windowed mode from that dialog, and see if the mouse works right. Scrolling also works as a mouse click on my linux system, as far as I know it has always worked that way for everyone... useful if you want to click a button quickly, like to train a level fast (though having to click like that should be a thing of the past after the next update)
