The couple share three children, twelve-year-old twins Hazel and Phinnaeus and ten-year-old Henry.
According to Radar, Roberts and Moder are having problems because of her recent 'romantic reconnection' with her former Pretty Woman co-star, Richard Gere.
A source told the publication, 'Julia and Danny have had their flare-ups over the years, but nothing like this fight. Danny was furious about Richard, and dumped out all his frustrations about their troubled marriage in one ferocious rant.'
Roberts also regularly posts pictures of herself with Gere to her social media accounts.
It is not uncommon, however, for Roberts and Moder to not be seen together. The couple regularly go long periods of time without being spotted together.
Earlier in the year the couple made a public appearance, but prior to that they had not been seen together in over seven months.