putting music on a san disc campact flash card?

I am trying to put music on my san disc compact flash card. It is a 2gb and I only have 110 songs on it. It says there is still 1.5gb left on it, but each time I try to put more music on it, it tells me that it can not create that file. But if I erase a song from it, it will let me put another one on. Can anybody help me, I cant figure it out. Thanx