3D View Weird Pivot

I have been working on a composition with FBX, deleting things, adding things and I have gotten into a situation where it is impossible to use the 3D viewer.

Take a look at this video:

The rotation, zoom, etc. is occurring around an unknown location a long distance from my model, but you can see my model is sitting right on the grid.

A single click of the scroll wheel moves the view a large amount.

I'm sure I have accidentally messed something up but what and how to do I fix it?

Thanks, Andy

I don't know if this is going to work, but you could try ctrl+F to fit the scene. Maybe this will reset the internal pivot as well.

Thanks Sander - Ctrl+F works! Andy