I have been working on a model all day, using the orbit tool on my mouse. Suddenly every time I use the orbit tool my model vanishes off the screen. Any ideas?
Click … Camera > Zoom Extents
Then as you orbit be sure to place the tool on the model, not in empty space.
Does that help?
Hi Geo
No its still doesn’t work and now the select tool doesn’t work either. I can draw a rectangle etc. but as soon as I depress the orbit tool the whole model vanishes 
OK Geo…suddenly it all works again! I have no idea whats going on but at least Ive got it functioning again! Thanks
SU tends to take a toll on scroll wheels and their buttons.
If it starts misbehaving again, try a different mouse.
You could try a 3D Mouse like Space Navigator or Space Pilot, etc. I recently added one to my SU workflow and it has helped reduce the time involved in modeling. This device greatly enhances rotate and orbit operations in particular with no effect on your existing scroll wheel mouse.
I was having a similar issue this morning - at times while editing a component or group things would rotate around a point local to the component or group, but all too often things would rotate around the context of the entire model, which could easily rotate the parts in question off the screen, requiring re-centering, panning, multiple operations, etc. Maddening! AND there is blessed little out there on this topic. Perhaps its a non-issue for most people.
What I finally found is that it is dependent on the current “extents” of the model. So, let’s say that you have a reasonable size site plan with a building, structure, roofs, etc. 80 feet x 150 feet - those are the extents. Now suppose that there is a small piece such as the base of a post, 24 x 24 inches and it is a component. If the extents of the model are near the extents of everything, you will orbit around a point within or that rotate the entire set of extents.
Now, edit the small piece and set your view to hide everything else. Orbit will still rotate as if ALL of it is visible. At this point press the Zoom Extents button or select it from the menu. Pressing the middle button for Orbit will now rotate more closely around the centroid of just this component. Took me a couple hours of futzing around, head-scratching, cursing, and research to figure this out, so I’m hoping others will find this eminently useful.
Thanks for sharing - good little tip.