Sub-assemblies are invisible in my drawing?

[JA5.15]

This has happened several times since I've upgraded to Civil3d 2014. I've created assemblies using generic sub-assemblies, and created a corridor. After closing and re-opening the drawing the sub-assemblies are no longer visible. The center assembly line is showing but no attach sub-assemblies are visible. The corridor is still visible, and functioning correctly, I can go to the assembly properties and see all sub-assemblies exist as I created them, but they are not visible in model space. I retain all functionality but it makes it near impossible to modify the assembly after the fact. It will even let me drag sub-assemblies out of the catalogue but they still are not visible in model space. 

Once in a blue moon it will pop up an error saying that it was not able to locate the catalogue and it displays a file path to one of my project dwgs that should have nothing to do with anything. Something is corrupt somewhere but I have no idea what. 

Using ACAD/C3D 2014,  Win7.

Any ideas?

[Jay_B]

Have you tried specifying a Code Set Style that is set up for displaying assemblies?