Both mine and my girlfriend's sight suddenly went black for a moment, as if we blinked at exactly the same time (in a brightly sunlit room).
It was the middle of the day, we were just talking in her room and suddenly, just for a blip, all we saw was black.

Is there an explanation for this?

How do you know you both saw saw black at the same time? Did you both mention it at the same time? Plus what were you talking about, the paranormal? I find this a very strange thing and can't quite grasp why this would be in the paranormal section unless you were both in touch with the same spirit, being shown exactly the same thing at exactly the same time, which is hardly likely.

Very odd. :)

Forgot to add it's possibly that for a second you were both slightly blinded by the sun, as you say it was a brightly sunlit room, so that's quite possible that you were both facing direct sunlight whilst you were talking to each other, but the paranormal side to it seems highly unlikely.