Any information on the fix? Please.
Why yes I do have the solution to this very annoying problem.
Basicaly, pay attention and read the following people
When the box is unticked in the Sound menu on World of Warcraft you are using the in-games sound crap (sorry for the lack of terminoligy here) NOT your creative x-fi. You may also notice certain sounds are missing ie when trying to mine a vein you dont hear the dink dink dink noise.
Ahah you say YES DAMONIC I HAVE THIS ISSUE..
Well people here is how you fix it, and why it happens.
It is not Creatives fault, nor is it WoWs, WoW is pretty old and its hardware is old, all this works great on Windows XP.
Firstly you need to download "Creative ALchemy" this software by creative basically restores sound from your Creative card that Vista no longer supports for games.
Once you download and instal that, fire it up. You will see World of Warcraft. Drag this over to enable "ALchemy-enabled games"
Now you have just restored all the missing sound you once had on XP.
BUT this still will not fix it as Patch 2.3 of WoW screwed this up.
BUT you can still fix this. (Am I getting annoying yet

)
Finally go into your WoW dir and find the wow.exe
-Right click and select "Properties"
-Click the "Compatibility" tab
-tick "run this program in compatibility mode for:"
-From the drop down box choose "Windows XP (Service Pack 2)"
OK everything and fire up World of Warcraft.
You have now fully restored the sound on Windows Vista and World of Warcraft.