Maybe a silly suggestion, but did you check the Material Room Simple view before adjusting anything? It might give a clue where that bright magenta colour is coming from. Is there perhaps a PoserSurface hidden behind PoserSurface_2 (in the Advanced view)?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)