See https://bugs.launchpad.net/ubuntu/+source/ghostscript/+bug/257854 The user is printing on a large-format printer with Gutenprint (a CUPS Raster driver). pstoraster only crashes on the biggest page sizes, so it seems that crash is related to the amount of data per page which has to be handled. Please contact the reporter of the Ubuntu bug for getting more information if needed.
Marcos will evaluate this one first
Retried with current Ghostscript (8.71) and the problem does not occur any more. All the recent fixes on the "cups" output device seem to have covered this one, too. Closing ...