some RRD graphs not drawn

Hi there,
I'm experiencing a problem with the rrd graphs of the disk space.
I'm running Hobbit 4.2.0 with the allinone patch on Debian Etch as server and the clients are BB 1.9c.
I have 2 Linux servers running with Veritas Cluster and reporting to the Hobbit server.
When I click on the disk icon of the first client everything is displayed correctly. I have all the mount points on top of the page and below them all mount points are displayed as graphs.
On the second machine some of these graphs are missing although they are displayed in the list on top and the RRD files are generated correctly.

Regards
Torsten