My sd card shows full when video recording but its empty?

i've just bought a 4gb micro sd card HC. i put it in my samsung phone and it shows the card in inside. i have no data at all on my sd card and on my phone i can take tons of pictures if i want. but-- when i try to video record, it tells me "memory full, delete some files" so i go on delete files and then it says "no files". how can i solve this prob?