Cube Icon Missing on Nav Bar

Indeed strange, I never saw this. Is this a vanilla installation or is there some customization in the instance. Just to be sure it is not a cache issue can you reset your user preferences ( 2016-08-29_1556 - SugarCRMSupport's library  ) in your user profile and as an Admin run a Quick Repair and Rebuild? Is this happening for one user or for more?

I have just had this same issue in version 11.01 and Since Gary's image is missing, I couldn't tell what to uncheck.

To resolve: 
1. Navigate to Admin > Display Modules and Subpanels.
2. Uncheck the Allow users to select modules to appear in the navigation bar check box, save.
3. Go and see if the problem is resolved.
4. Then go back in and check it again and save.

I have just had this same issue in version 11.01 and Since Gary's image is missing, I couldn't tell what to uncheck.

To resolve: 
1. Navigate to Admin > Display Modules and Subpanels.
2. Uncheck the Allow users to select modules to appear in the navigation bar check box, save.
3. Go and see if the problem is resolved.
4. Then go back in and check it again and save.