There is a bug with the ARROW tool in the Draw toolbar. If you draw an arrow straight up or down (rotation 0 or 180), a division by zero occurs and you end up with geometry rings containing null/NaN values in the coordinates, resulting in a malformed polygon that extends from your point of origin to the prime meridian.
A workaround would be to check the geometry for null/NaN values before putting the graphic on the map. JS greasemonkeys out there can probably patch this on the prototype, but a fix from ESRI would be nice.
