Hello,
Sometimes it happens that the Start Menu making the screen "hang".
So for example; when you open start menu, all is OK
When you close start menu, the size of the start menu stays blurry visible (transparant)
So you have constantly your left bottom screen filled with blurry transparent in the size of the Start Menu.
After that you can again open the Start Menu again and it works OK but when it closes its again blurry.
The fix: Log off and Log on and it works properly again. It already happened sometimes.
Any idea? I try when I see it again, to make a screenshot.