[BretMan]

This runner was obstructed while rounding first base. Generally, when a runner is obstructed while rounding a base you can consider her to have been obstructed between that base and the next one.

If she's obstructed while rounding a base, as soon as she passes it won't she still be on an obstruced/altered path? If the obstruction is right at the base, it's virtually impossible for the runner's basepath to return to normal, as if the obstruction never occured, the instant that she passes the base.