I think that the poor short-term memory and black-outs are directly related to too much happening in the mind at any one time. Stress and anxiety would probably be at play on the side too.
I only experience black-outs when I am out walking through the city (Dublin, Ireland). I could be walking and then suddenly stop, forget where I am and what I'm doing... ...and then everything returns about two seconds later.
I guess these black-outs could be seen as being like a head-rush. Do ye get me? During a head-rush you get up too fast. During a black-out we are thinking (Obsessing) too fast.
yfguitarist, I also sometimes nearly fall down during a black-out. I never have but I just stumble. Again, it's probably just the brain going into overdrive. The central-thoughts in your head are stealing all the energy and starving other parts of the brain responsible for regular functions.
... ...It's the psychological version of 'tripping-up'.