It sounds like the cable and/or housing are dirty or frayed. Try disconnecting the cables and operate the calipers and brake levers independently by hand. The source of the binding should be easy to isolate that way.
What make and model of brake do you have? Newer Shimano models can have the pads adjusted for toe-in and Kool Stop makes pad holders for either Shimano or Campy brakes that allow toe adjusting with out resorting to bending the arms.