I'd say yes, something is scaring him. It could be anything though - even the smell of his aftershave, or whether he is wearing boots, or is (not being rude) quite loud.... My sister was here a few weeks back, and my timid cat, who really doesn't like strangers, was very much at home with her - my nephew's staying this week, and No.1 Son won't come in the living room at all, he's hiding out in the garden most of the time. Rover's all over my nephew, so it's very much an individual cat thing.