As Tom pointed out you need to add the hostname, but if you already doing this then the help page http://www.logicmonitor.com/support/monitoring/os-virtualization/troubleshooting-wmi/ has a section on repairing wmi counters.
"You may be experiencing unexplained errors such as "Empty result set", ox80041003, 0x80041017 from the collector debug, WBEMTEST utility, or your custom application."
There are steps to repair your counters in that help page, I have found this cures the empty results set problem in all cases I have seen.
Microsoft state that this may happen when "... certain extensible counters corrupt the registry, or if some Windows Management Instrumentation (WMI)-based programs modify the registry", but the exact nature of these issues is largely unknown and normally not worth troubleshooting extensively.