There is a very common mistake when fastening the cable to the front derailleur - many front derailleurs have a washer with a little tab under the pinch bolt. When connecting the cable it seems to make sense to run the cable under the tab, but this effectively shortens the lever on which the cable is pulling, and so the cable has to be under much higher tension to make the derailleur move. The cable should be routed over the tab, then bend sideways under the pinch bolt. The result of doing this wrong often gives symptoms just as you described.