THANK YOU for finding that bug. It got past me. What happens is most text boxes in the game have dialogue ID numbers and the one for saying "You're carrying too much stuff!" was not only the wrong number, but it was well beyond the range of the dialogue, causing the game to freeze. It did not just affect the chest in the lava caves, but all chests in the game, should you have full inventory.
It should be good, now!
I don't know if you will be able to continue the game, though. When I did the update, I lost the save files on my end. It was kinda screwy when I did it, so I can only hope that a) others don't lose their files and b) that will never attempt to do an update that dumb again and just stick with updating the filename as-is (While I have some years of making HTML5 games, I am a total newb to posting them anywhere outside my own domain).
