Black screen on browser

I flashed the proposed RC3 rpi3 image and ran it with a hdmi connection to a Multisync EA243WM screen with no ethernet and a usb mouse. On running the browser (from the home screen) I got a blank screen (with a thin purple line down the lhs just to show it was still active), couldn't get any menus to appear. I power cycled it and the second time running the browser I didn't get a black screen but on going back to the home screen all the icons were black squares http://i.imgur.com/IJZjLDh.jpg - also black squares on the pop out menu. I've not - so far managed to replicate this