Tonight, for the first time in four weeks, this test (#6) passed on Darwin/PPC. Cf.: http://smolder.plusthree.com/app/public_projects/tap_stream/8270/260
I can't really tell which commit fixed this failure. Given the fact that several files with 'pack' in their names were changed in r32888 (particle changing PARROT_API -> PARROT_EXPORT), that commit is a possibility. Assuming it continues to pass over the next week, I will close the ticket.