I'm having some troubles with the materials in the viewport. This has happened in two different files (and for different materials & objects in the same file).
Materials "disappear" from some objects (but not others). The materials come back if I toggle Edit mode (but not if I toggle rendered view on and off).
Please note that these are not materials or objects that I have worked on this session (the materials were assigned to the objects when I opened the .blend)
(I've also have issued with the viewport not updating when doing changes to the material [Material caching disabled]).