Help how do udowngrade to gb?

hey guys i rooted for the ics beta, but it gave me so much problems that i want to downgrade it... i did follow the instructions online and got odin and SGH-I727-UCKJ2-k0nane.7z and i followed the steps and unrooted. for some reason though, i keep getting errors and it won't let me open any apps... anybody know how to fix this?