Hi Steve, this generally means that your zoom approached close to the pivot point.

When that happens, MoI will slide the pivot point forward along that direction so that you can continue moving forward. It is difficult to get the traveling speed completely the same when it switches gears into "slide forward" mode, that is likely to be the kind of speed change that you are experiencing there.

I added this "slide forward" mode into MoI to solve the problem in Rhino where zooming in the 3d view only approaches the pivot point and never goes past it - this tends to cause a confusing kind of "halt point" where you can only come up close to the pivot and never go past it to something on the other side, no matter how much you keep zooming in.

You can set the pivot point to a specific point by using the "Area" zoom button on the bottom of a viewport - that center point that you click for that zoom rectangle will become the rotational pivot point. Also if you want to get it to the center of a selected object, then Reset will do that.

- Michael