Couldn’t get the WDTV to login to my Windows 7 file share; kept complaining about not being able to access it. Finally resolved it by changing the following parameters in the registry to tell Windows to utilize enough memory to be a fileserver:

Set the following registry key to ’1′:
HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\LargeSystemCache

and set the following registry key to ’3′:
HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\Size