Black streaks when printing on 4x6 photo paper

Hello. My printed photos have black streaks when printing on 4x6 photo paper. The paper used is HP Vivid Photo Paper Matte. I successfully printed 50 pictures before the black streaks began to appear. The streaks are thin, vertical and about one inch long. They do not appear on print-outs using regular paper. I've tried cleaning and aligning the printer as well as changing the print cartridges. I'm printing from a PC using Windows 7. A wireless connection is NOT used. Any help would be...

Black streaks when printing on 4x6 photo paper