Traffic statistics won't work

[zeopha]

My system :FC3
SNMP:net-snmp-5.1.2-11
Cacti:cacti-0.8.6c
I want to monitor my PC's traffic.when added a new graphics and implemented 'Verbose Query' ,it returns follows:
+ Running data query [1].
+ Found type = '3' [snmp query].
+ Found data query XML file at '/var/www/cacti/resource/snmp_queries/interface.xml'
+ XML file parsed ok.
+ Executing SNMP walk for list of indexes @ '.1.3.6.1.2.1.2.2.1.1'
+ No SNMP data returned
+ Found data query XML file at '/var/www/cacti/resource/snmp_queries/interface.xml'
+ Found data query XML file at '/var/www/cacti/resource/snmp_queries/interface.xml'
+ Found data query XML file at '/var/www/cacti/resource/snmp_queries/interface.xml'

and in my /etc/snmp/snmp.conf ,there are statements as:
view systemview included .1.3.6.1.2.1.1
view systemview included .1.3.6.1.2.1.25.1.1

so i think my configuration confilcts with interface.xml
when I replaced the interface OID with 1.3.6.1.2.1.1,it won't say 'No SNMP data returned' .when I do "Turn On Graph Debug Mode." it shows:
RRDTool Says:
ERROR: opening '/var/www/cacti/rra/traffic_traffic_in_20.rrd': No such file or directory

In the data template of interface-traffic,there are just one traffic-in and one traffic-out

does cacti 0.8.6 require specific snmp version?
any helps will be appreciated.