Right click menu - select world plan. Or press ctrl + w.
pressing the shift key, and the right mouse button (possibly by accident), rotates the view.
## Edited ## just been looking at your drawing, and it is getting a bit stretched in the 'z' coordinates, although its all 2D (ish), you have the main drawing somewhere around z = 0. There are objects with z = -49318mm (some grouped with object at z = 0), obviously not causing a problem, but just thought I'd mention it in case you hadn't noticed. ## End Edit ##