The solution I found to this after reading through all the forums on this issue is -- You have to right click in the viewport on the objects that you can't select. In the right click menu click Activate Class & Activate Layer. Even though my layers and classes were set correct I was still unable to select all the objects in the design layer.. Randomly only a few in the layer were selectable.. Nothing else worked until I did that right click and Activate Class + Layer. After that I switched the class & layer options back to S/S/M+O ( Show/Snap/Modify Others). Strange but it worked.
This somehow got my file workable again.. Hope this helps.
