Unity4 -> 5 some assets in project but not rendering

I have tried upgrading a v4 project twice now to v5.

Many assets are there in the Hierarchy and Project but not rendering.

Whats up with that?

It is a pretty bizarre effect.
The objects that are not rendering are appearing in the Hierarchy.
I can select them there and there wire frame highlight appears but no textures are rendered.
The textures do appear in the Inspector and all the settings look

Very weird.
I am guessing that I just have to rebuild the project.
But of course I would much rather not.