It would probably help to get some debugging output from the hobbitd_rrd module. Do a "kill -USR2 <hobbitd_rrd PID>" and it will start logging debugging output to the logfile. The next time your Mac OS X client sends it's data, you should hopefully get some info about what it tries to do. Repeat the kill-command to turn off debugging.
I have run that now, The strange thing is that I have 2 hobbitd_rrd processes... I have run the kill -USR2 on both of the PID's I will post the data once I get it
The error that is coming up is in rrd-status.log and it is
[date] [time] Host '[hostname]' reports vmstat for an unknown OS
Using UNAME I get the following information: Uname -a Darwin [hostname] 8.3.0 Darwin Kernel Version 8.3.0: Mon Oct 3 20:04:04 PDT 2005; root:xnu-792.6.22.obj~2/RELEASE_PPC Power Macintosh powerpc
Thanks,
Adam