Quite a few things I would think:-
a) - he hates grass
b) - the weather and conditions are pretty appalling and everyone seems to be miserable
c) - he's probably tired after Rosmalen
d) - he always acts like that when he's losing or having a hard match anyway
And yes I'm interested too Paul - in what way have they treated him badly at Wimbledon? Mind you, imo, Wimby never treat anyone particularly well - that's why a lot of the players don't like it.