Mental Ray's driving me Mental!!: Can't get smooth fade outs to work

[chigwedere]

I'm fairly new to 3d modelling so I hope this problems not really a problem, but it has already consumed a lot of my time.

Problem: Object in viewport has a visibility track added to it via track view (or 1st keyframed in object properties). Bezier interpolation handles ensure a smooth fade out of the object over around 2 seconds.
A) Scanline Render of fade animation = works perfectly (pruducing avi, qtime, tiffs etc that show the animation working as set up, giving a smooth gradual fade out)

B) Mental Ray render of fade animation = object WILL NOT fade out smoothly at all but 'cuts' out at when value reaches 0 in track view graph, as though the bezier interpolation is completely ignored.

Objects used: range from simple box primitives, sphere primitives to an image mapped plane primitive, nothing fancy.

Same results with Max versions 7, 8, 9 and 2008

Please help, anybody!!

[3dartist]

I just joined this forum but it doesn't seem to be very active. Unfortunately I can't help you with the problem.