It sounds like either a bad cable, or a cable that isn't the correct spec. Have you tried a different cable? Cheaper HDMI cables work well for short lengths, where interferrence, and other things don't come into play. HDMI's Maximum certified cable length is 49 feet, with a category 2 spec (better shielding and such) The Maximum length of a category 1 spec is about 16 feet.
My experience with HDMI boosters is about 50%. They either work well, or they don't work at all.