[ubuntu] Desktop has gone blank

I have installed ubuntu 12.04 LTS on virtualbox(host os Windows 7). It was running fine after installation except that it was 1024X768 instead of 1366X768. But after installing the guest extensions as prompted by the OS itself, it went fullscreen(1366X768). But everything else like the icons and status bar at the top went invisible. They are still there and can be used with guess work.

Thankyou for your support:)