If you remove “Windows Essentials” Windows Live Essentials" “Windows Sign In assistant” , your shares will work on WDTV Live.
In my case, I had just installed Windows Essentials for email and movie maker and one other program…Anyway, there was no un-install option for “Sign In Assistant” which was reported to be the culprit for shares not working on WDTV Live.
So I just removed the whole kit n kubutle and my shares now work on WDTV Live…FYI
Actually, a good discussion on that here:
Windows 7 shares and WDTV Live
WDTV Live password error when connecting to windows 7 shares