disk graph strangeness

Hello,

I've a host that's picking up all kinds of oddness on its disk graph.  
The data seems correct, this is from client data:

[df]
Filesystem         1024-blocks      Used Available Capacity Mounted on
/dev/sda2              1951832    659176   1292656      34% /
/dev/mapper/root_vg-var   5242716   4405508    837208      85% /var
/dev/mapper/root_vg-usr   2097084   1328888    768196      64% /usr
/dev/mapper/root_vg-home  12582524   8865656   3716868      71% /home
/dev/mapper/root_vg-varlocal 131067996 117865944  13202052      90% /var/local

but the graph looks like this:


I've never seen such bizarreness on one of my graphs.  The last two 
lines are particularly creative.  Any ideas how i can track this down?