I have had it happen. Usually a Bugsplat will shortly follow. Even if it does not and you can recover or undo to the point before the error became apparent, go to Window menu>Model Info>Statistics>Fix Problems immediately. Usually some huge list of errors will show up.
At one point, I found this happening a lot and found it was tied to a Ruby (since deleted, so I don't know if it is the current one of that name or not) for selecting all instances of a component at once. If the Ruby was used on a component while inside another component and when there were instances of the first component outside the current editing environment, bad things like this could happen.
On the other hand, sometimes it just happens. Be sure to turn on hidden lines if you try to fix it...there tend to be odd ones, nearly infinitely long, floating around.