Does Rmpfr_get_str() work any better ? Or perhaps you can simply print $barray[$i], "\n"; ('print' uses 'Rmpfr_get_str'). The overloaded functions use defaults, so you would want to first set the default rounding mode to GMP_RNDD if you use print().
I'll try to fix this over the next couple of days - I haven't yet managed to reproduce the problem on Win32 (and haven't yet tried on linux).
Thanks for the report.
Cheers, Rob Update: Included some code tags, missed earlier