Well, the obvious place to start is - do you get any events on the devices that aren't graphing new data such as SNMP Agent Down?
* as you copied over RRD files, make sure you didn't break filesystem permissions to $ZENHOME/perf/Devices for your non-graphers.
* Check log files. If they don't show anything, change the daemons to use debug logging for a little while and restart zenoss - see if anything is useful there...
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James Pulver
ZCA Member
CLASSE Computer Group
Cornell University