I just downloaded MX Player, then installed the ARMv7 Neon codec, played MX Player and it downloaded the ARMv7 codec. It seems to happily recognise almost all of the films on my Acer, which is very strange as it wouldn't play any of them.
I have the same film on the internal and the external SD card - it plays that version on the internal but not the external. It will play some of the films on the external, so it isn't a problem per se with the SD card. I also have a TV series in a folder on the external SD card and just episode one of that series on the internal. Again, it happily plays the one episode on the internal but will not play any of the episodes in the folder on the external. I am guessing that it has an issue with a folder inside a folder on the external but am yet to test it by dragging an episode out of the folder and dropping it straight on the card. I did try to do that with long hold and move but the A500 had a bit of a moan about that.
Well, my new Asus TF201 arrives tomorrow afternoon so I look forward to having all of this fun all over again with another machine!!!