RiJaa
Comments
Humor us and try it without Optifine.
I would also like to point out that this is a very recent issue. I had no issues with this a month ago. From what I gather this might be as recent as last week. I cannot prove this though. This issue, unlike MCL-6280, has not been an issue for over a year.
This issue is different from MCL-6280, as sounds are no longer working on any version up to 1.5.2 (and go back as far as alpha versions of the game), and it doesn't matter if you do this on the native launcher or on the java launcher. However, minecraft 1.6.+'s sounds work fine, leading me to believe that this is a seperate issue.
TL;DR: Sounds not working both in native launcher AND Java Launcher. 1.6+ works fine. Anything below not.
Regarding Avoma's question, this specific issue does not generate a crash-report. I usually get this issue on first startup of the day. Second startup and subsequent startups during the day do not have this issue.