I had to revert back to 2.9.1 again for like the 3rd time - every time I update something breaks.
This time, the player stopped working on the single post view - the player just disappeared - it was there then when you click to play it disappears, leaving a sort of line. Very odd. Seemed to work fine in the index page though, although oddly all styles (using the MediaElement.js Skin by Premium Pixels/One Design - yes I tried it without, didn't fix it) weren't showing.
Even tried adding the Addtype for SVG as suggested here: AddType image/svg+xml svg to htaccess - didn't fix it.
As before, reverting to 2.9.1 did - works fine and even shows the proper HTML player in Firefox (it was oddly showing the 'default' HTML5 player, which won't work with the mp3 file I was using.
I'm sure can't do that forever as browsers move so quickly but what gives?