I am doing an animation where a character bends over and picks up a large placard. He holds it up for a few seconds and then bends over to put it back down. He stands up again and continues hand-gesturing without the placard.

Simple in theory. The placard (a simple Poly Cube) is parent-constrained to one of the character's hands. The visibility is "off" until he picks it up. The visibility is "on" for the duration of him holding up the card, and keyed to "off" again when he puts it back down.

The problem is when I render out my frames (.tiff format, using Mental Ray) , the damn placard is still visible AFTER it is put down, just sitting there at the bottom of the screen! (if anything, it should continue to move with his hands, as it is parent constrained)

For the record, it looks fine when I do a single frame render in Maya, and it works fine when I playblast the scene. It only glitches when I do a full-fledged batch render

There are a few possibilities here. I turned off default lighting in my render globals. Would THAT make a difference? I can't think of anything else.

I will add pictures when I get back from work tonight, but ANY help would be appreciated!!

Thanks in advance!