Scarlett Johansson is seeing red!

Though she's currently ad exec Nate Naylor, 38, The Avengers actress "is pissed" her ex-husband Ryan Reynolds has moved on with his Green Lantern costar Blake Lively, 24. "Scarlett cut off all contact with Ryan," a source tells the new issue of Us Weekly (on stands now).

Johansson, 27, had once hoped to rekindle her romance with Reynolds, 35, but she now knows that "he and Blake are very serious."

For more on how Reynolds' new relationship has devastated Johansson, watch this week's Hot Stuff video, as told by Us Weekly senior editor Ian Drew -- with very special guest Carrie Keagan from VH1's Morning Buzz.

Also in the roundup: new couple Amanda Seyfried and Josh Hartnett double date with on-again loves Jennifer Carpenter and Michael C. Hall, Nicole Richie fetes celeb trainer Tracy Anderson at her L.A. baby shower, and much more!