There could be several possible reasons for such a behavior.
- Guest OS issues - e.g. network driver not loaded properly (check Windows event logs)
- Physical network configuration issue - port security enabled on the switch port(s)
- Hypervisor issues - which virtual network adapter do you use
To find out whether such an issue might be related to the physical network, try to ping another VM on the same host/port group. Also take a look at the physical switch port(s) configuration and make sure it's configured properly (in case of a managed switch).
André