DSTT...'Menu?' or blank screen

today, i wanted to switch a game on my dstt so i turned it off and turned it on again, then the screen went all white???
searched the web, tried deleting some games, turned it on again and there was a word 'menu?' with and sad face on top ???,
:mad: i went back to look at it on the comp and all the files was washed away, nothing!!!! :( wat the hell is happening to this card :confused:, i need help anyone out there, i need some recommendations pleeaaase for my card to work.
p.s ds works (i tried brain training and it worked), dstt works (tried putting it in my ds without the memory card and it works), but im not sure about the memory card (first in the comp all the files was in place, then when i deleted some games, unplugged, tried, plugged, it wasn't there) :(:(

right now it's all blank, says nothing, no sound just white screen