Black fuzzy line on pictures when using external flash?

I received a brand new external flash today (Yongnuo Flash Speedlite Yn-460ii for Nikon Canon Pentax) for my Nikon d3000. The flash works great but there's a black fuzzy line at the bottom of each of the pictures. Can someone help me fix it?

Added (1). If I bring my shutter speed down too low the photo becomes blurry.

Are you shooting in sync with the flash? If you are shooting too fast you may get a blacked out are… Try 1/60 - 1/125.

Your using too fast a shutter speed. All cameras have what they call the 'X' speed, the fastest shutter speed you can use where all the sensor is exposed, usually around the 1/180th to 1/250th of a second depending on camera, the 'X' speed will be in your cameras spec.

Read the manual - especially the part about external flash. Read the manual that comes with the flash. It may have something to add on the subject.

As stated in both answers above, you are setting the shutter speed too fast. If you set it to the camera sync speed you will have no more problems.

The flash will freeze the image. You should not have blur at 1/125.

Comment: "there's a black fuzzy line at the bottom of each of the pictures"
Answer: You are probably using too fast of a shutter speed (read your manual to find out what the maximum flash sync speed is. That is the fastest speed you can use with flash).

Comment: "If I bring my shutter speed down too low the photo becomes blurry"
Answer: Then you need to hold the camera steady. Or use a tripod.