I hesitate to ask this question since it seems so basic but... when drawing an arc at the end of a line, I used to be able to move away from the end point of the line, move back to the end point and be in the arc function. Now when I move away and back I just get more lines. Is there a parameter I may have inadvertently changed?
Nothing has changed but make sure you're not clicking/releasing the mouse button but keep it pressed. Other way is to press A when you're drawing lines and this would toggle between Line to Arc.