What kind of cables did you use? First, I'd make sure the cable housing slid fully into the groove in the brake hood. Some cables come with ferrules that are too large to fully slide in. This could be causing a kink or something.
Also, make sure you cut down the cable housing to an appropriate length. If the cable loop that goes right into the barrel adjuster of the RD is too short this could be a problem. Make sure all your cable housing cuts are clean and haven't ovalized the end as well.