If you have upgraded to Ubuntu 12.04 Precise, you will notice the Alt key does not work in EL. This is because it has been hijacked by Unity's HUD. To disable the HUD, I used Ubuntu Tweak. You can get it from the ppa at:
https://launchpad.net/~tualatrix/+archive/ppa
(with instructions there as to what to do)
Or you can download from their website:
http://ubuntu-tweak.com/
Then in Ubuntu Tweaks go to: Tweaks->Unity. You will see the option to turn off the HUD at the top of the page.
As an aside, you can also turn off the Ubuntu log on sound in the Sound option on the Tweaks page.