My girlfriend has 2 nights in a row, had an episode where she blacks out. It's not so much a loss of conscience, but she goes into a blank stare becoming completely unresponsive when I'm talking to her. This lasts for about 30 seconds.
While that would be troubling enough, once she comes to, she acts very childish and slow-minded responding to any sort of stimulus. I'd compare it in all honesty, to a drunk 14 year old. She's 23. It took her 1 full minute to remember only part of what happened 10 minutes prior to the blackout.
Over the next 1-2 hours, she gradually comes out of it - albeit very groggy - slowly returning to her normal self.
I'm extremely concerned about this matter.