now get partial black screen after log on and welcome screen Recently upgraded

[newtusmaximus]

  HP DC7700 Ultra Slim factor Desktop
model name : Intel® Core™2 CPU 6300  @ 1.86GHz
model name : Intel® Core™2 CPU 6300  @ 1.86GHz
Architecture:          i686
CPU op-mode(s):        32-bit, 64-bit
*-display
      description: VGA compatible controller
      product: 82Q963/Q965 Integrated Graphics Controller
      vendor: Intel Corporation

Updated to LL2.6 from 2.4 via menu/settings/ Lite Upgrade.
Initially no issues on boot start up
Recently  now get partial black screen  after log on and welcome screen. Get xcfe bar at the bottom, but rest black – i.e no background picture and no icons.
http://i.imgur.com/AEFzFHk.png


Otherwise all working OK  I.e browser, mail etc.
Home folder / linux desktop shows that folders within the desktop are still there and can be activated etc.


Actions taken.
Menu/settings/Display – all appears OK – Monitor still identified and correct resolution.
Menu/settings/appearance  seems OK @ MediterraneanWhite
Screensaver set to blank screen only – unchanged - not locked
Power manager – On AC  PC activate after 17 min idle.  Monitor = sleep after 7 minutes and power down after 17 minutes inactivity.


No other programs added since upgrade to 2.6
Any ideas. Tks