Problem with Mapped Drives? Help, Please!

So, I have a Western Digital My Book 1.5 TB hard drive connected to my Asus RT-N66U router, and it seems to be losing connection? Under Windows 7, it mapped perfectly, and was always accessible, but now after upgrading to Windows 8, it won't stay mapped.

I'll restart my router and computer and it will be connected, but after a while (time varies), it stops the connection and I get this error message:

An error occurred while reconnecting to (drive letter):
Microsoft Windows Network: The local device name is already in use.
This connection has not been restored.

Here is a screen shot of it.

All my other computers - one running Windows 7 and two Mac's, both work with it perfectly.

I have Kaspersky Internet Security installed, but have tried disabling it. Any help please?!

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