There could be several reasons, major ones being:
DISCPLINE of the view. If this is set to anything other than Architectural or Coordination, the building model is shown as halftone and is partially transparent. If there is an object in the linked file "over" the top of your family, you won't be able to select it. To check this, change the view properties discipline to Architectural or Coordination. If you then cannot see your JB, that may be the problem.
DESIGN OPTIONS. If someone is using Design Options on your project and the JB is on a design option you are not editing, you won't be able to select it. (normally it would also be greyed out)
Selection could be achived by:
Changing your view:
Discipline
to Wireframe
using a Selection Window
hth
Simon