AV Out will not work correctly on WDTV Live

  I have also held the reset button on the bottom of the unit down for about 15 seconds to see if that would change anything - it did not.

Bad idea – it did change something.  The reset button has two functions.  If you hold it in for one second the player reboots and returns all settings to the factory default.  (You can also do this with the remote).

If you hold the button in for 10 seconds or more you change the player from US (NTSC) to Europe (PAL) video format.  If you live in US, you changed it to Europe.  Now, assuming you did this only once, do it again for 10 seconds and return it back the way it was.  Hopefully, things will improve.  Go ahead and reset to factory defaults for the one second press.

Now, since you found the WD forum website, go find the support section at www.wdc.com , find your player model and download the complete user guide – you’re gonna need it.