Graphs Empty - Nan Values

I know this has been out there before, but I haven't found a resolution yet.  I have zenoss 3.2.1.  None of my performance graphs are registering data.  I've tried several different browsers.  SNMP seems to be working just fine.  WMI is also set up.  Also the values listed say NAN.  This is not a new install and so it's had plenty of time to go through the cycles to get the data. 

Any suggestions??

Thanks,

Lauren