Talk to the hand, because the head has issues.
I've always interpreted it as meaning, "there's stuff going on that I don't want to tell you about, so leave me alone." Or if you're using it to describe someone else, it means, "there's some problem with xxxxx, but I have no clue what it is - and rather than find out, I'll just say he/she has issues so I don't need to get overly involved in whatever those problems are."