I'm having the same problem and I've had ad sense for 2 years. Suddenly...no ads. It works on this page http://www.moonsmusings.com/lbdarling/holiday/ but when I try to put the code on nearly ANY other page...nada.  I'd love to cancel my account but not looking forward to Google holding onto money it owes me just for general purposes.  If anyone has any clues I'd be grateful especially since these 'people' can't be bothered to address problems they create themselves. Yes, I'm a little bit angry. :)