Question about sharp aquos lc40e77u line down middle of TV

I just recently bought this model 1 month ago and just yesterday noticed, while watching a standard definition tv channel, that a line shoots down the middle of the screen when red, orange or yellows are around the middle. When I changed to an HD channel to see if it was doing the same thing I couldn't see it. So to clarify ...I get this line down the middle on SD channels on RED, ORANGE and YELLOW colours. Should I be calling up Sharp asking to a replacement or repair? Or does it maybe have something to do with my cable. Also to note, I don't have an HDMI cable running from my cable box to my TV...just components that give me decent quality HD picture, could this also be a solution? Thanks in advance!

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