Changed any settings or added any new addons lately? And just in case make sure the sound is actually turned on under the video on youtube. I don't even know how you would exclude chrome from running sound on it's own. Is it just youtube?
I rebuilt my computer and it was working at the start, but then it went away. Everything else has sound - even Youtube in Firefox. I googled it and apparently there is a bug with Flash 11.3 and apparently 11.5 as that is what I am running with Youtube in Chrome. Was hoping anyone had any insight
Uninstall flash and reinstall it. If that dosn't work hunt around for an earlier version of flash and see if it still does it. If none of that works only thing you can really do is wait for a bugfix. I can tell you that it works fine for me but that doesn't really mean much.
Or check to see if Chrome got assigned to one of your digital outputs instead of the main speaker outs. When in Chrome watching YouTube, right click on your audio icon in the bottom right corner. Select "Playback Devices". It will look something like this: Check to see if Chrome is playing its audio on another device besides your normal output.
You can switch Youtube to use HTML5 instead of flash last I checked, pretty sure thats what I have mine set to. Flash is a dog most of the time anyway.
I tried it all. I installed Flash 10 and it still isn't working. The sound doesn't seem to be coming from anywhere else. Like I said the sound works for everything else, including Firefox. Odd.
Just out of curiosity have you tried changing the sample rate/bit depth in the speaker properties advanced tab? Also try checking the two boxes in that tab as well if they are not checked.