I still can't record my guitar using Cool edit pro but found another way around.

I use the creative recorder from my sound card and it works.

I do use the mic jack but disable the option to amplify the sound (+20 db). I didn't have this aoption with my old card.

I tried the line in and don't have a lot of success with it. I'll try to look more into this but as of now, everything's back to normal. Well, almost :)