Fox's official 24 website, and 24.Wika.com have pretty much confirmed it. Curtis Manning is dead.
However...like last season with Tony, we'll probably have to wait until next week's episode, or a later episode, for his death to be confirmed.
In any case, Curtis' character will definitely be missed.
"Growing up my dad was like 'You have a great last name, Galifianakis. Galifianakis...begins with a gal...and ends with a kiss...' I'm like that's great dad, can we get it changed to 'Galifianafuck' please?" -- Zach Galifianakis