I can move the ball in every direction except for down, i've tried everything possible, thanks to the forum, but nothing works. is there a way to navigate the icons by using the keyboard?
nope, only in some specifically designed games will keys operate as arrows.
I don't know what all you have done, but to review:
--remove the battery and reboot.
--Blast it with air
--force the downward motion with firmer pressure on the trackball
--clean it with some rubbing alcohol, LIGHTLY applied with Q-tip.
--disassemble and clean.
This happened to me a couple of weeks ago! Very annoying. i did a search here and found the same suggestion JC says (depressing the trackball and rolling it in the busted direction).