Problems with mumamo and ps-print-buffer-with-faces

Hi folks,
When I try to use ps-print-buffer-with-faces mumamo throws an error and 
fails to apply the faces to the output! Same goes for ps-print-region-* 
and ps-spool-*. The error is in mumamo-fontify-region - "Just changed 
major, should not happen". The file consists of HTML with interspersed 
PHP.
Has anyone any ideas what's going on? Has anyone got it to work?
Many Thanks
David


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