Thanks Tim,
Clipping becomes an issue when you have very large overall extents. e.g. one object close to 0,0,0, and one object on a survey grid.
It can also be an issue if you have a relatively large dataset and you are trying to look in a tunnel or other small space within that large dataset.
There is a long and boring explanation as to why this happens which i have long forgotten, but I can tell you that we have implemented a near clipping plane animation parameter that will be included with the next release. There is no date for this release yet, but I will post on this forum when we find out.