Lighting changes somehow?

I am new to Unity and am having a problem with a project I am currently working on. The lighting in the game view and scene view suddenly changed and I can’t seem to find the cause.

This is what the game did/should look like:

This is what it looks like now:

Each time I open the project it looks like the first image, but there is a progress bar in the bottom right of Unity, that on completion changes everything to the second image.

Progress bar:

Any ideas what may be causing this and how I can fix this?

This is due to Unity’s lighting system. It takes about 2 minutes or so (for a decent sized project) for the lighting system to calculate/bake the lighting after you open your project. You wouldn’t have noticed it in Unity 4.x because Unity now uses a new lighting system. It’s perfectly natural for your lighting to do this as far as I know, and is just a price one has to pay for having GI (Global Illumination) and PBR (Physics-Based Rendering).