MacBook Pro not outputting audio Yesterday I could play music and actually hear something, but as of today, my MacBook Pro speakers aren't producing any sound at all. 

Here is what I tried:


rebooting (a cold reboot too) several times
internal/external speakers
PRAM reset
Reinstall iTunes
Using headphones


There is no red light in the headphone jack.

The only thing I did was updating my iTunes to the new 10.5.3 version. But I doubt this is the cause because other programs aren't reproducing any sound too. So, no sound at all on my MacBook Pro (mid 2011). Any idea or hits to get the sound back?

EDIT
And to make it even more weird, the mail-app is making sound when sending and receiving mails. But iTunes, QuickTime, VLC, Safari,... These apps aren't making any sound at all!
In the first instance, please repair disk permissions. If that makes no difference please try starting your machine in Safe Mode before restarting (back to normal mode) and seeing if that made any difference.

If neither of these work I would reinstall the OS over the top at this stage.

As to the cause? I think the Quicktime system plugin has incorrect permissions, is damaged or just plain isn't where it should be. Let us know how you get on!