I have not seen this one before. 1.) Zoom extents 2.) Switch to an isometric view (e.g., SW Isometric) 3.) Switch back to plan view 4.) Zoom extents. Now all of my drawing objects are in the upper right corner of the drawing window at a very small scale. In other words, the drawing window appears to be empty except for a tiny speck in the upper right corner. There are no other objects in the drawing. I am using C3D 2014.
I attempted to recreate this issue in Civil 3D 2014, and was only moderately successful. I followed the steps you outlined, and my zoom extents after switching to an isometric view were about 1/2 to 1/3 farther away from the model. While this was noticeable, it was not exactly as you described.
Does the data in your drawing actually move, or is this strictly a zoom extents/view problem?
Does this happen to all of your drawings?
No, the data does not move. I haven't checked other drawings to see if this is an isolated incident, but I don't recall seeing this behavior before.