In Windows 2008 and Windows 2008 R2, especially with older cards and drivers, you may experience very high latency to client/guest OS especially when copying files or using network related services but the host itself has normal netowrk responses. this can be caused by the Virtual Machine Queues (VMQ) setting in the configuration of the physical network adapter. go to the properties of the addapter, then select Configure:
Next, on the Advanced tab, scroll down until you find Virtual Machine Queues or VMQ and make sure it is disabled:
click OK on both property windows. it will that a moment for the adapter to reconfigure but after a minute or so, the network should function normally.