printing on fredrix inkjet canvas

[pinkpetunia]

I'm getting a horizontal line every 1" down the page forming a horizontal grid. I'm using fredrix inkjet canvas an epson RX595 printer and photoshop cs3. There doesn't appear to be a way to change the paper thickness settings. Do you have any suggestions on how I can fix this problem? I have cleaned the heads and aligned them and still have the same problem. This line does not appear when printing to regular paper. Also, the line it is printing is the correct colors, just very dark, so I ruled out a single head plugged issue. Thanks in advance for your help, Carol