I think it REALLY bothered Heo Young Saeng that Kim Hyun Joong did not thank SS501 during his thank you speech at the 45th Baeksang Award ceremony because he mentioned it during a show he appeared in. Click on link to view article: Heo Young Saeng upset with Kim Hyun Joong. I think the show where HYS mention this is "KBS Star Golden Bell".
I like Kim Hyun Joong a lot, but as I watch him on screen more and more, I feel like there is a side of him that isn't so great. I was a little bugged when I saw his acceptance speech that he did not mention SS501, but I kind of let it slip my mind when you said on a separate occasion that he will be with SS501 to the end. But some how I still have this nagging feeling that there is more to him than what he shows on the outside. There have been multiple occasions where the other singers leak out little bit of his personality and it confirms to me that he is not as nice a guy as we might think. I think he can be pretty rude and arrogant with the people he is close to--like the other SS501 singers. There is a "tough" side of him--the don't mess around with me side. But we don't see that side because of etiquettes. Oh well this is just a hunch, I would have to meet someone he is really close to if I really want to confirm this (like that will ever happen), but I am almost 100% positive that there is a side of him that is not so pleasing.