MAXIMUM NUMBER (128) OF SHADER KEYWORDS EXCEEDED
After having a load of problems with running out of shader keywords 'Maximum number (128) of shader keywords exceeded' - sound familiar?
Anyway sometime ago I wrote a tool that helps dealing with it. I call it my 'Shader Keyword Tool'. Not so much of an issue since 5.5 as they increased the count to 256, but for anyone who would find it useful it can be found here.