Have had similar swings myself, it definitely is too small of a sample size to say if it's variance, bad play, a ghost, or anything in between. That's your actual profit though right? Do you know or can you find out your EV ROI or luck adjusted winnings, that does help a bit in figuring out what's going on. I've only grinded 500 sng's since I've started, and I've had a 45 BI down-swing in one 80 game stretch, my graph looked just like yours, though I was running really poorly and when luck adjusted math was looked at, I should only have lost 1/3rd of that.
Have you read this article?
http://www.pokerstrategy.com/strategy/sng/1072/5/
Some of the statistics are sobering, or comforting. Either you realise how rough SNG play can apparently be, or you take solace in the fact that it's not uncommon to have a stock-market crash 1930s depression style graph once in a while ♦
The site I am playing on, betfair, is part of the ongame network, and they seem to have quite a bit of traffic on the "rookie sng holdem games" which have an 10+1 cent buyin. I can't comment on the quality though.
Hope it swings back up for you, I have felt the pain my friend.
G.