>It's worth pointing out that default Samba/SMB settings even on some high-end well-regarded NASs are not always compatible with all Windows functions e.g. http://forum.qnap.com/viewtopic.php?f=189&t=48793 . However, in your particular case I'd expect an SMB misconfiguration to result in an operation failure rather than a long delay but eventual success.
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>I like Gregory's idea about checking power saving states. For the NAS that would be disks/network connections/overall device. You may also need to check the Windows server; it may connect to the NAS via a different NIC and that NIC may be set to power-save. Some so-called "green" switches or routers may also power down "inactive" ports.
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>In my experience I have never seen a case where power saving in a server environment is worthwhile. All it takes is one foulup caused by an inappropriate or too-aggressive power saving setting and the time it takes to troubleshoot it costs more than all the power that might be saved over the lifespan of the device.
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>I imagine power saving settings are useful and reliable with enterprise-grade equipment in large datacenter environments but that's not my line of business. For small/medium business usually the best bet is to go through the settings in detail and completely disable all power saving features.

Thanks, this is some very interesting information.