LOS ANGELES: Needless to say, it's been a difficult month for Janet Jackson.

At the memorial service for her late brother, there were rumblings about the absence of longtime boyfriend Jermaine Dupri and we can now confirm why: the couple has broken up.

"His friends are telling people it's over," a source told Us Weekly, while another chimed in: "They have been moving in different directions for a while."

So, what was the cause of the break-up? Conflict over the fact that Dupri produced several of Jackson's recent singles, reportedly.

"You shouldn't mix business with pleasure," said a friend. "Janet felt their lives were too crossed and they should have kept things sepa­rate."

As for Janet's reaction to brother Michael's death? Things haven't gotten any easier for her, said a source close to the situation.

"She's devastated. She's busy caring for Michael's kids. Janet's the family's backbone."