Did your nozzle check/test print come out clean for the black head?
Depending on your art setup, you may be getting a rich CMY mix producing a faux black.
When printing, does it make the motions like it's trying to print the crop marks, but doesn't?
Most notably is the speed difference, it will kick in and do a standard speed print, pause, then if you're in high quality it will switch into high quality mode which is a noticeably slower and less noisy print speed.
Only other thing I can think of to mention is when you go into your settings, make sure you have the image selected in the preview pane, it will have a blue outline around the image/what you're cutting, then go to Marks and making sure Crop Marks is checked. I've had some issues with losing my selection before and scratching my head trying to figure out why options are greyed out/not functioning right because the image wasn't selected.