Sexpot SCARLETT JOHANSSON’s crying on the shoulder of former on-again, off-again hunka-hunka JUSTIN TIMBERLAKE about her failed marriage to RYAN REYNOLDS – and that’s making TimberSnake’s still ring-less girlfriend JESSICA BIEL CRAZY because she fears Scarlett might try to get Mr. SexyBack BACK!

Said a source: “Scarlett was hot and heavy with Justin right before falling for Ryan, and now that Scarlett and Ryan are divorcing, Jessica is terrified the former lovers will pick up right where they left off. After all, he dated Jessica and Scarlett simultaneously at one point. Jessica’s always looked the other way and given Justin his space when he needed it. They’d be apart for a while, then get back together. But now she’s worried that’s all going to change with newly single Scarlett back in the picture.” Stay tuned.