1. An interpolated image generating apparatus that generates an interpolated image to be inserted between a source image and a destination image, the apparatus comprising: a motion estimating unit that estimates a motion vector from the source image to the destination image; a first calculator that calculates a motion vector reliability level indicating reliability of the motion vector serving as a vector used for inserting the interpolated image, a value of the motion vector reliability level being determined in such a manner that the stronger a correlation is between an area in the source image and an area in the destination image that are brought into correspondence with each other by the motion vector, the larger is the value; a second calculator that calculates a failure-preventing vector reliability level indicating reliability of a failure-preventing vector that is a predetermined vector used for preventing image failures; a correcting unit that calculates a reliability ratio that is a ratio between the motion vector reliability level and the failure-preventing vector reliability level and corrects the motion vector reliability level and the failure-preventing reliability level in such a manner that the closer the calculated reliability ratio is to 1, the smaller the value of the motion vector reliability level becomes and the larger the value of the failure-preventing vector reliability level becomes; and a blending unit that obtains a motion compensated image by performing a motion compensating process based on the motion vector, obtains a failure-preventing image by performing a motion compensating process based on the failure-preventing vector, and generates the interpolated image by blending the motion compensated image and the failure-preventing image according to a weighted average of the motion compensated image and the failure-preventing image that has been calculated by using a weighting factor based on the motion vector reliability level and the failure-preventing vector reliability level.