GGNFS on PPC

Does anybody have any tips/experience on compiling and running GGNFS on PPC?
It (version 0.77.1) seems to compile for me (gcc 4.0.0 darwin8) in pretty much the same way as on a Lintel system, and runs similarly, too, for input numbers up to about 80 digits, but then above that, on PPC I get fatal errors that do _not_ appear on Lintel.
The errors are all at the start of the sieving stage, and of the form:
"warning: not enough polynomials in mpqs with 121051732500949"
(It would seem the same sieve executable - gnfs-lasieve4I12e - is being used as for the smaller inputs that complete successfully)