Aero Peek Alt-Tab problem in Windows 7

In Windows 7, I had an annoying problem with Alt-Tab. After pressing Alt-Tab, the window containing the thumbnails of all applications disappeared due to "Aero Peek". In fact, the window containing the thumbnails disappears to the background because "Aero Peek" is showing an another Window on top of it. This problem was seen on two machines (a laptop and a desktop). On most machines it is working fine.

 I could not resolve the problem for now, but as a workaround I have turned off "Aero Peek":

1. Start Control Panel
2. In the search box, type "Performance Information and Tools"
3. In the left panel, click "Adjust visual effects"
   
4. On the first tab "Visual Effects", disable "Enable Aero Peak"
   
5. Click "Apply" or "OK"