Z
Dear,
I understand your frusteration, however playing online is all about honesty and fair play, that has to be commited by the players themselves.
Just to show you a point; what if a high rated player is just using a chess program all the time to analyse and choose his moves?? nothing... We are here to have fun and enjoy the game and friendships about it.
For this case, just ignore the guy later on, as long as you believe he did so on purpose.
Additoinal Info about the topic; I was mistaken saying there is nothing to be done. I found out yesterday, that you can report the player, you thing, that they are cheating. The site admins would make their own work trying to prove it or not. If he is caught, his account will be cancelled.
According to the forum, you just report Abuse ( the link should be available by bottom of the page ) and you should do so in privacy, not publicity.