We have this one (or a related one) on the internal bug tracker - from what I've seen so far, it looks like if Noise maps are used in more than one channel / material, then changing anything about the Noise makes the material render yellow until IR is restarted. Changing the Noise did used to cause a crash, but doesn't seem to any more (for me, in the Beta 2 RC1, the crash seems to have stopped). I've added a link to this thread to the internal bug report, so that the info here can be taken into consideration (and hopefully we can reply here when we have a fix for it :) )