Failing to poll a device for a config change usually indicates a problem with the ccmHistoryStartupLastChanged or the ccmHistoryRunningLastSaved objects from the CISCO-CONFIG-MAN-MIB (assuming an IOS device). Many versions of IOS have problems with these objects, but that is not really a problem. If polling fails, RME will default to fetching the configuration.
To troubleshoot, you can run a sniffer trace on a device which is failing and/or enable ArchiveMgmt Service debugging under RME > Admin > System Preferences > Loglevel Settings then look through the dcmaservice.log for issues.
