Why can't i load a .GIF file into after affects to use in a composition?
And what would solve this (to get some similiar effect)?
You can. You may have to check file interpretation and loop to footage to use it. Many animated gifs are only 2 frames so they won't play and you won't be able to extend the length unless you loop the footage.
Here's a list of all supported file types in CS5.
Retrieving data ...