I found an interesting scenario that causes the invalid ID/Password combo with my WDTVs
If I do any significant updating of content on my network shares, i sometimes find that the WDTV loses connection to these shares and I have to reboot the host PC to get back connections.
I noticed this while I was copying older legacy smaller hard drives (500 gig and 1 TB drives) into a newer 4 TB drive that will store much of my music.
After I copied the data to the 4TB drive (which was a recognized Network Share) I lost the connection to that host PC and had to reboot to reconnect via my WDTV Live.
This isn’t a big problem for me, but I’ve noticed it a few times when making changes to a network shared drive.