We seem to have a regular problem with our new 7556 printing out pages that have the intended art missing and replaced by out of register colors from the art randomly spatteryed accross the page or just a portion of the art and black lines that run down the entire page. Sometimes after doing this the printer will just reset itself and then be fine again.
In order to get this type of behavior all I have to do is send over a large multi page document and instead of letting the printer print it immediately I tell it to hold the job, or if the printer is out of paper and holds it for resrouces, and when the data sent to the printer gets up around 900 Megabytes the problem will show itself. The first pages will be fine, but then after a while it will go nuts.
I have had service come a few times so far and they first thought it might be overloading the RAM, but then said it should store the files on the hard drive so that the RAM wouldn't be overloaded by a file that is a couple gigabytes at most. They also thought it may be something in the postscript that was causing the problem, but it seems to happen with dozens of different files. I have even printed Indesign files that were just pages of .jpg images and the only postscript was the type on them, yet it still had this issue.