In Windows 7, when using mapped drives on a laptop, you may find that after moving around (undocking, connecting via Wifi etc.) that the mapped drive becomes a zombie – it still exists, but is essentially dead. This seems particularly prevalant where offline folders are used. This appears to be caused by the network drive service starting before the network connection is necessarily stable. However, you can change the behaviour with a simple registry key.
add a new DWORD entitled RestoreConenction
Set the DWORD value to be 0
After a reboot, network drives will only be reconnected to when you try to access them through explorer or the file system APIs.