For interest, please post an MGADiag report - I suspect it may show what the problem is...
we need to see a full copy of the report produced by the MGADiag tool
(download and save to desktop - http://go.microsoft.com/fwlink/?linkid=52012
Once saved, run the tool.
Click on the Continue button, which will produce the report.
To copy the report to your response, click on the Copy button in the tool (ignore any error messages at this point), and then paste (using either r-click/Paste, or Ctrl+V ) into your response.