50 Cent Now BEEFIN' with Dr. Dre...WHY???

50 Cent says Dr. Dre is upset with him for launching his own line of Sleek by 50 headphones, which are competing with the Beats by Dr. Dre line. The Doc is apparently so mad that Fif' claims he won't be on Detox.

Although 50 was upset at first that he and Eminem weren't brought in on Dre's initial headphone deal, he's gotten over it. He Tweeted, "Okay, I'm done talking about Jimmy and Dre. I love them, and they hate me -- so what? [Eff] it."