Cycles : Materials turn black


Any idea why some textured materials turn black when rendering with Cycles ?
Seems to happend when having many textures, is it due to CUDA textures limitation (64 colored and 32 b&w) ?
Does anybody else meet this problem ?

i think here is a limited number of textures:
max 100

About this there is a bug submission to the tracker: 30472


Ok thanks for this info