If you get the Advanced network test error "unable to load performance counters" and you are running from an administrator account, then it may be that your system performance counters are not available.

The advanced network test requires the Windows Performance Monitoring to be enabled (it is by default) for the “Network Interface”.

Try running the Windows “perfmon.exe” tool to see if you can see the “Network Interface” performance counters. If you do you can add it using the “+” button to add a new counter, and select the performance object Network Interface, Bytes Total/sec.

If you can't see the Network Interface performance counters, then you can rebuild the performance counters using the 'lodctr /R' command in an open cmd prompt window.