Not sure if we are experiencing the same thing but I had similar symptoms on a Windows Vista pc. This doesn’t sound like the issue the linux folks were having.
I installed the drive, let it do the initial backup etc without problems. The next day I went to copy a file directly to it and got the write protected message. Drive properties, security properties etc. all showed that I should be able to write to it.
What I eventually found was that it was protected by the drive security encryption.
I opened up the WD Smartware software and the drive status showed that it was locked. Clicking on the drive icon prompts you for the security password and the drive was available again.
I haven’t experimented yet to see when it gets locked down but I suspect it does when it goes into power save mode.
One concern I have is how will the automatic file backup work unless each of my family members goes in and unlocks the drive before they make any file changes which is unrealistic.
