The phenomenon (doo, doo, do, do, do, phenomenon, do, do, do doooo - sorry, having a muppett moment there
)
Let's start again...
The phenomenon is known as 'Gimbal Lock' and is a product of the calculations that Lightwave uses to compute its rotational angles. I don't pretend to know all the theory, so this page should give you more than enough information:
http://www.anticz.com/eularqua.htm
Unfortunately I can't tell you how to get out of a Gimbal lock situation. Anyone else here have an answer?