animated file textures in layered shaders...(mabey just using renderman for maya, not tested in other renderers)
An image file sequence on a surface shader, nested in a layered shader can fail to update in batch renders. Fix this by having the same file in node plugged into a lambert attatched to a single tiny polygon occluded inside or behind another object in the render (dosen't work with the object hidden). The file in will update with the lambert and this will force update the layered shader, they share the same input.
-- RyanHarrington - 01 Mar 2008