The Problem
have you seen Netmeter keep notifying you that Nothing to monitor. Well, you may find this article useful.
The Condition and probable cause
Upon Installation of Virtual PC 2007 on Vista, some network services are also installed which as it is apparent prevents programs like Netmeter to evaluate network interfaces. In this situation the program fails to discover network interface despite you have at least one of them on your PC. (e.g Wireless).
NOTE Some networking features of vista may also affected with Virtual PC.
No remedy identified so far. keep one of them, uninstall the other.