The LaserWriter Utility wasn't designed to print out the configuration page on a LaserWriter Pro 810 from the utility itself. You need to turn on that feature by using the utilities, then restart the printer. Although LaserWriter Utility 7.6.1 was revised and intended to be used with the LaserWriter Pro 810, the problem you describe occurs when you have a fax option card installed in the printer, resulting in the PostScript error message. LaserWriter Utility 7.6.2 fixes this problem.
More specifically, the LaserWriter Pro 810f printer is not listed in the table of printers supported by the LaserWriter Utility v7.6.1; after the utility launches and checks the characteristics of the target printer, it detects the fax option card, assumes incorrectly the type of printer being queried, then enables the wrong menu options to be displayed. When the Print Configuration Page is chosen, you'll get the error mentioned. When the LaserWriter Pro 810 has the Fax card installed, the following menu items are available in the LaserWriter╩Utility 7.6.1 "Utilities" menu:
Name Printer...
Set Startup Page...
Get Page Count...
Print Configuration Page...
Download PostScript File...
Restart Printer...
The following is the list of menu items that should be displayed:
Name Printer...
Set Startup Page...
Get Page Count...
Imaging Options...
Download PostScript File...
Restart Printer...
Change Zone...
Paper Handling...
Along with the fixing the menu items listed, the LaserWriter Utility 7.6.2 software also added support for the LaserWriter Select 360-J (the Japanese version of the LaserWriter Select 360).