nagvis not creating graphs for all performance data delivering probes

I have added nagvis to my nagios install, enabled graphics and automatic creation of graphs. I can see graphs created for /dev/hda1, /dev/hda2, but not for /user, /var/lib/mysql mounts. These deliver perfdata:

/users=5889MB;4128489;4644550;0;5160612
/var/lib/mysql=25941MB;120948;136066;0;151185

I the bacula plugin delivers performance data too:
Files=43;;; Bytes=6.684MB;;;
Files=19;;; Bytes=4.307MB;;;

But no graphs are created.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: nagvis (not installed)
Uname: Linux 2.6.39.3 x86_64
Architecture: amd64
Date: Thu Jul 14 13:49:19 2011
ProcEnviron:
 LANGUAGE=de_DE:en
 PATH=(custom, user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: nagvis
UpgradeStatus: Upgraded to natty on 2011-05-21 (54 days ago)