An object in your page uses the setgray command in an improper fashion. This error could be caused by tints in your lay-out, or by imported EPS files.

In the Print-menu of Macintosh, you can define that you print to a black-and-white device or to a grayscale/colour device. For imagesetters and printers, you should always select 'grayscale/colour'. Failure to do so can also generate the above error.

Fonts created with really old versions of Fontographer can also cause this type of error. Switch to other fonts or resave these fonts in a recent version of Fontographer.