When I click on a jpeg or tiff thumnail, instead of opening in photoshop the thumnails open in windows picture viewer. I am using CS6 extended on windows 7. I first noticed this when I tried to download from creative cloud to CS6 Photo opened in Windows. I called support (CHAT) and they couldn't help me.
Go into Bridge, and choose Edit - Preferences - File Type Associations (Bridge - Preferences on Mac).
Try setting the individual type associations you want to point them to Photoshop. If that fails, try the [ Restore Defaults ] button.
You may have to log off and on again to get preference changes to take hold.