problem on getting performancecounters from server computers

Question

I am accesing to all off the computers on my lan and geting performance counters, but some of server computers doesnt give me true values they returns 0. is there any setting for this? note: firewall status is close for servers.

here is a code sniplet from my application:

 PerformanceCounterCategory pcc = new PerformanceCounterCategory("Network Interface", ipAddress);                   

 string instance = pcc.GetInstanceNames()[1]; // 1. network kartı  
 PerformanceCounter bandwidthCounter = new PerformanceCounter("Network Interface", "Current Bandwidth", instance, ipAddress);
 PerformanceCounter pcReceived       = new PerformanceCounter("Network Interface", "Bytes Received/sec", instance, ipAddress);
 PerformanceCounter pcSent           = new PerformanceCounter("Network Interface", "Bytes Sent/sec", instance, ipAddress);