The rear brake cable hocks onto a lever in the backing plates on each side. It may be that one of these connections came apart on the wheel that spins. You can check this by pulling the cable away from the backing plates. If it comes out then in wasn't connected and will have to be. This is all that I can think of.
2005 Deep Beryl Green WK 5.7L Hemi: QD II/ SRT8 shifter, petals, roof rails, wheels, grille, rear Brembo calipers, rear sway bar and springs/ body color mirror covers/ Xtreme HID 4300 Dims and Fogs/ Cabin Filteration Kit/ shorty antenna/ SC Flashpaq 91 tune/ full LED interior and partial exterior/ BWoody 4" CAI/Stillen headlight covers/ partial de-badging/ My GIG w Lockpick/ 22Elite leather console cover. Mods to come in the Spring: WK bilsteins, SRT springs, Bwoody end links and Brembo calipers for the front.