There are two important numbers - the check interval of your Check_MK service (normally 1 minute) and the value for staleness in your global settings (default 1,5). A service is shown stale if no check results are arrive in the given interval. In your case the agent looks like working normal but you get no valid information for CPU utilization and Disk IO. That can have many different reasons. As booth values are fetched as performance counters i would say it is very likely that you have a problem on your Windows server with the performance counters. First step i would test is update the agent on this machine to 1.6.