50 Cent and Fab has been going back and forth because of a comment Fabolous Made on Twitter, you can follow that here .  50 addressed their  current status on an interview with MTV:

“Yeah, we’re cool,” 50 said recently on the set of his video for “Baby By Me.”Fab particularly is an artist I’ve interacted with twice. He’s [opened] two international runs [for the G-Unit]. It wasn’t specifically to try and help him broaden his international presence, but it obviously it would help for him to be there and be in front of the audience internationally and put his best foot forward first. Give a good show and people become Fabolous fans at that point.”

Honestly I dont think Fab wanted beef with 50 anyway playing it neutral has worked so well for him all these years.