"There was a problem playing this item." error

Hi Guys,

Trying to view media stored on an external wireless HDD (WD mybook live) via Plex.

PMS finds the files/metadata, but when trying to play back the file either within PLex.Web or via chromcast/plex andriod app, I get the There was a problem playing this item. error.

I have tried:

re-naming file to preferred naming convention

re-loading data

moving file to new location and re-adding to PMS

uninstall/reinstall latest version of PMS.

This seems to happen to about 3-4/5 movies, and about 2/5 TV series I try to view.

I have attempted to load the log file (could have completely muffed it up).

Current versions:

Plex Web 2.1.12

Server 0.9.9.7

Mac OSX 10.9

Android 4.3

Plex android app version 3.3.2.137

Please advise as Plex seems to offer so much more than when we were using Apple TV.

Thanks in advance.

Chris.

[attachment=32849:Plex Media Server.log]