No sound

Hi!

Since last update (1.8.1), I have no sound at all in Minecraft.

I get "missing pack.mcmeta" in the resource pack menu, under the default resource pack. Error messages also show up in the launcher under the "Game Output" tab. e. g. "[15:51:37] [Client thread/WARN]: Unable to play unknown soundEvent: minecraft:gui.button.press".

So far I've tried: Deleting all Minecraft files and reinstalling everything, same with Java (both 32 and 64 bits were tried, separately and together), running an earlier version, using the F3 + S shortcut ingame, playing in fullscreeen vs windowed, deleting and reinstalling openAL32.dll and openAL64.dll

All sound hardware and software work flawlessly on my computer, I get sound from all other programs and Minecraft isn't muted in the Mixer neither. Also, I don't have any mods/resource packs installed.

Thanks a lot for your time!