Let's have a look in the syslog:
Jul 15 12:45:01 exodus /USR/SBIN/CRON[13409]: (root) CMD (if [ -x /usr/bin/mrtg ] && [ -r /etc/mrtg.cfg ]; then /usr/bin/mrtg /etc/mrtg.cfg >> /var/log/mrtg/mrtg.log 2>&1; fi)
Jul 15 12:45:01 exodus /USR/SBIN/CRON[11878]: (root) CMD (/usr/bin/mrtg /etc/mrtg.conf >/dev/null 2>&1 )
Jul 15 12:45:01 exodus kernel: grsec: signal 11 sent to /usr/bin/mrtg[mrtg:21264] uid/euid:0/0 gid/egid:0/0, parent /bin/bash[sh:11878] uid/euid:0/0 gid/egid:0/0
Jul 15 12:45:01 exodus kernel: grsec: signal 11 sent to /usr/bin/mrtg[mrtg:31263] uid/euid:0/0 gid/egid:0/0, parent /bin/bash[sh:13409] uid/euid:0/0 gid/egid:0/0
Jul 15 12:46:56 exodus kernel: grsec: From 192.168.1.5: signal 11 sent to /usr/sbin/dpkg-preconfigure[dpkg-preconfigu:18818] uid/euid:0/0 gid/egid:0/0, parent /bin/bash[sh:14918] uid/euid:0/0 gid/egid:0/0
Jul 15 12:46:57 exodus kernel: grsec: From 192.168.1.5: signal 11 sent to /usr/sbin/dpkg-divert[dpkg-divert:29794] uid/euid:0/0 gid/egid:0/0, parent /var/lib/dpkg/tmp.ci/preinst[preinst:21015] uid/euid:0/0 gid/egid:0/0
Jul 15 12:47:43 exodus kernel: grsec: From 192.168.1.5: signal 11 sent to /usr/sbin/dpkg-preconfigure[dpkg-preconfigu:13142] uid/euid:0/0 gid/egid:0/0, parent /bin/bash[sh:14529] uid/euid:0/0 gid/egid:0/0
Jul 15 12:47:44 exodus kernel: grsec: From 192.168.1.5: signal 11 sent to /usr/sbin/dpkg-divert[dpkg-divert:4315] uid/euid:0/0 gid/egid:0/0, parent /var/lib/dpkg/tmp.ci/preinst[preinst:20065] uid/euid:0/0 gid/egid:0/0
Anyone an idea, what happens wrong?