That is very strange, I wonder if it could just be the browser caching an old version and the two are conflicting in some way? have you tried clearing the cache for the game's website? It still would be odd that is is both Firefox and Chrome unless you have ran it on both previously and they both have a cache issue. I tried loading it and it works from my previous save and also after clearing the save via the menus. It works for me in both browsers, hmm. If that doesn't work could you open the console with F12 and see if any error message is printed there. I also think the sound issue is related since that seems to be okay for me also.