Halo 3 Skull Problem?

[Virus Magnet]

I am trying to get all of the skulls on Halo 3, But when i get the one from the very first level at the start (i'm not sure what one it is again) I pick it up and nothing happens. Is this meant to happen? If not how do i get it so it's unlocked?

Also the same thing has occured on the Crows Nest level with the skull in the pipe. The first time it wasn't there, but then i started mission from beginning and it was there, but when i picked it up again nothing happened! Can anyone explain how to fix it and if this may happen again and how to fix that?

Thanks in advance

 

[Amanda]

Do you already have those particular achievements? If you don't and you think that it's a glitch within the game, restart the level/the 360 and try to grab them again. It should work fine for you as it has for me and countless others.