[Wintermute]

Mendacious, look up the standard deviation in your win rate of BB/100. Divide it by sqrt(5)--that's the CLT at work--and I suspect you'll find that win rates of -40 BB/100 are not that unusual for 500-hand samples, probably just over a single std. dev. of the mean. (May be more severe for you if you have a less variance-susceptible style of play in comparison to me, as I would imagine.)

You will experience much worse episodes of running bad, and for much longer--it's an unfortunate consequence of poker.
(As you know, however, the reverse effect--bad players having relatively frequent spells of running good--is what keeps the pond stocked.)