Problems Developing Driver for Seiko SLP-100

[Alex Satrapa]

We're currently trying to set up a CUPS driver for the Seiko Smart Label 
Printer 100. We've set up a PPD that details the available label (paper) 
sizes, but for some reason the log files are showing that CUPS is trying 
to print to A4. Not only that, but the print job ends up dying with an 
erro, "Error: /undefined in tSaR":

 From /var/log/cups/error_log:
D [...] [Job 17] cups->header.Duplex = 0
D [...] [Job 17] cups->page = 1
D [...] [Job 17] cups->ppd = 0x89fb3a8
D [...] [Job 17] cups->ppd->flip_duplex = 0
D [...] [Job 17] width = 221, height = 703
D [...] [Job 17] PageSize = [ 79 252 ], HWResolution = [ 201 201 ]
D [...] [Job 17] HWMargins = [ 0.000 0.000 0.000 0.000 ]
D [...] [Job 17] matrix = [ 2.792 0.000 0.000 -2.792 -0.000 703.500 ]
D [...] [Job 17] Error: /undefined in tSaR
D [...] [Job 17] Operand stack:
D [...] [Job 17]
D [...] [Job 17] Execution stack:
D [...] [Job 17] %interp_exit   .runexec2   --nostringval -- 
--nostringval--   --nostringval--   2   %stopped_push   --nostringval-- 
   --nostringval--   --nostringval--   false   1   %stopped_push   1   3 
   %oparray_pop   1   3   %oparray_pop   1   3   %oparray_pop 
.runexec2   --nostringval--   --nostringval--   --nostringval--   2 
%stopped_push   --nostringval--   --nostringval--   --nostringval--
D [...] [Job 17] Dictionary stack:
D [...] [Job 17] --dict:1053/1417(ro)(G)--   --dict:0/20(G)-- 
--dict:68/200(L)--
D [...] [Job 17] Current allocation mode is local
D [...] [Job 17] Last OS error: 2
D [...] [Job 17] ESP Ghostscript 7.07.1: Unrecoverable error, exit code 1
E [...] PID 2741 stopped with status 1!

Can anyone shed some light on this issue? Where should I try looking 
first to figure out why the RIP has decided to render for A4? What is a 
tSaR, and what does it mean when /undefined is found there?

Hope someone can help
Alex Satrapa
Australian Phenomics Facility