Interesting thread! We have similar situation!
Well, my hubby didnt invite his one of schoolmates Frank to attend his 50th birthday party at New Year Eve 2004 whom they grow up together since kindergarten due many reasons.
First of all I never like him for a long time but I has to respect my hubby´s friendship with Frank. I did told my hubby that I had the feeling that Franz is not real friend but he doesnt listen me.
We know for almost 2 years that Frank stabbed our back eg but we ignored it and thought it´s just kind of "gossip"/"misunderstand" rumor until we witnessed it ourselves at my hubby´s other childhood schoolmate Richard´s 50th birthday party in Munich last July 2004. We were on other table and watched Franz stabbed us to people where he sat on the table to share with them without notice that we WATCHED them and said NOTHING and carried on enjoy ourselves because we dont want to spoil Richard´s party.
Well after that, we realized that "gossip"/"rumor" is true so my hubby decided to not invite Frank to attend his 50th birthday party. We saw Frank again at Xmas party last 2nd week of December. We ignored his nasty remark. We thought he would come to us and have a talk to my hubby but he didnt. After Xmas party over, I suggested my hubby to write a nice letter enclosed Xmas card telling Frank how he felt and why he didnt invite Frank eg. My hubby told him that he find it´s sad what Frank did to us etc as long as he thought Frank is his friend. He is willing to have a open talk with Frank if Frank really want to. We sent a card with letter to him.
We received fax from him saying that he got our letter and throw our letter & card away to rubbish bin. I said to my hubby: It´s fine whatever he wants then leave him alone and also told my hubby that I find Frank´s behavior is very childish.
Sad situation.
Anyway, I can image when I was in Frank´s shoe. I would say something instead of playing offence, miserable, e.g. when I notice that my best friend or good friend doesnt invite us to attend their special occassion. Open talk is important to solve the problem and see each other what we made the mistake eg than play offense, sour, etc.