...if it's a wired connection, then it can be a 'Power saving' issue.
Did you disabled the 'Power saving' feature of your Network card? "The
Allow the computer to turn off this device to save power setting, controls how the network card is handled when the computer enters sleep and can be used if a driver misrepresents how it handles sleep states."
< That may be the key of your problem, if this 'feature' it's not working as it should...
>
Here you have instructions on how to disable it, for Windows 7 and Windows Server 2008 R2: https://support.microsoft.com/en-us/kb/2740020(Please report back if this solved your issue, since it may be of help as reference to another users having the same issue).
