Flatten chicken to 1/2 inch thickness by placing between two sheets of heavy-duty plastic wrap and hitting with a rolling pin.
Sprinkle with salt and pepper, then dredge in flour.
In a large nonstick pan, melt margarine over medium high heat, add chicken and cook until done, about 8-10 minutes, turning once.
Remove chicken from pan and keep warm.
In a separate bowl, mix broth and cornstarch until smooth, add the marmalade, and mix well.
Return empty pan to stove and add cornstarch mixture. Stir constantly over medium-high heat and cook until thick. Add balsamic vinegar, lower heat to medium, add chicken to pan, and cook 1-2 minutes, turning to coat evenly.