I think I understand what you did. You only key the armature motions (probably only rotations or IK target locations) in pose mode. The actual forward motion of the whole armature is keyed separately. If you want things to work properly, you’ll have to remove the location keying from the walkcycle action.
What harkyman says is 100% true. my brother was having the same problem.
Also, the ‘center’ buttons are NOT AVAILBLE for bones, no in edit mode neither in pose mode, check for yourself !! 8)
If you absolutely need to change the center of your armature you can create ANOTHER aramture (with the center where you really whant it) and then join the old one with the new one, but that will erase ALL constraints in the old armature.
Finally, for attaching the cape to your character, YOU DON’T NEED to attach it to the armature, you could just attach it in vertex level to the body mesh. Select the cape, hold Shift and select the body, enter edit mode, select 3 (very importat, 3) vertex of the body, press Ctrl+P and choose MAKE VERTEX-PARENT. Trust me, it work just fine and you don’t need to re-do the walk cycle.
(But re-doing it in the correct way would be the righ and proper thing to do )