My girlfriend has occasional "black" outs.. what's wrong?

She has these moments of blanking out, not actually blacking out but fainting and waking up, spacing out I assume. I never seen it in person but it happened while on the phone, she suddenly stopped talking. She said she gets a "bad feeling" then blanks out. She is aware of it when it happens. It also happened a couple of years ago while she was driving and it got her into a wreck. What is the condition called? Is it curable or treatable?