Strange RRD tool error logs

[neo14]

hi!

I've got some strange RRDtool error logs on my pfSense 2.1 box:

during startup (only on the console, not in any logfile):

Generating RRD Graphs...ERROR: Dangling Content
ERROR: Incompatible file version, detected version . This is not supported by the version 0003 restore tool.

after startup in the system log:

May 5 12:10:51 	php: : Creating rrd update script
May 5 12:10:51 	php: : rrdtool restore -f '/var/db/rrd//wan-traffic.xml' '/var/db/rrd//wan-traffic.rrd' failed returning 1.
May 5 12:10:51 	php: : rrdtool restore -f '/var/db/rrd//wan-queues.xml' '/var/db/rrd//wan-queues.rrd' failed returning 1.
May 5 12:10:51 	php: : rrdtool restore -f '/var/db/rrd//wan-queuedrops.xml' '/var/db/rrd//wan-queuedrops.rrd' failed returning 1.
May 5 12:10:51 	php: : rrdtool restore -f '/var/db/rrd//wan-packets.xml' '/var/db/rrd//wan-packets.rrd' failed returning 1.
May 5 12:10:51 	php: : rrdtool restore -f '/var/db/rrd//system-states.xml' '/var/db/rrd//system-states.rrd' failed returning 1.
May 5 12:10:51 	php: : rrdtool restore -f '/var/db/rrd//system-processor.xml' '/var/db/rrd//system-processor.rrd' failed returning 1.

(newer entries come first)

And when shutting down the machine, it's not logged in the local system.log but just on a remote syslog server:

May  5 10:48:38 pia kernel: pid 29198 (rrdtool), uid 0 inumber 2080 on /var: filesystem full
May  5 10:48:56 pia kernel: pid 42414 (rrdtool), uid 0 inumber 2084 on /var: filesystem full

Those logs (system states, processor…) are alway empty on startup.
other RRD graphs are not affected.

BTW: /var is not full. could it be unmounted too early or something?

does anyone know what's happening here?
should I try to delete the problematic .rrd and .xml files from /var/db/rrd?
I'm using the following snapshot: 2.1-BETA1, NanoBSD Size : 4g, Built On: Thu May  2 00:35:59 EDT 2013

thanks!