xaml design doesnot work - visual-studio-2012

Question

i can't see any control in xaml designer , i can click on them and go to behind code but can't see then , i reinstall VS 2012 but no luck , even if i create new project it will do the same , and this happen with blend too . i searched so so so so much to solve this problem , but no luck , please help me
PS : i installed vs 2010 sp1 , vs 2012 update 1
here the basic code of blank windows store app with a button
<Page
x:Class="App6.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:App6"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
</Grid>
</Page>

Answer 1

AT LAST after 5 days searching . i found the problem , it was from my video card :
i have hp probook 4540s laptop , it has intel and amd video cards ,so i customize the setting to give me full graphics power , so i open Catalyst Control Center and made the Power give me Maximize Performance (and here the problem started) i changed it to Optimize Performance and all came back to normal (OMG)

Answer 2

This is a guess, but you normally have to give the grid some kind of row or column definition. Here is a grid that defines two rows:
<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Button Content="hello world"></Button>
</Grid>
The above works for me, but the following does NOT work:
<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
<Button Content="hello world"></Button>
</Grid>