Also, why did they shut off deposits since then?
because there are only so many coins on the order books on each exchange. it just so happened, if you wanted to sell 3000+ coins on BTCE at any price available this morning, you can take it down to $100 in a quick 10 second period before it corrects/ new orders are filled in the books and it goes back to normal-ish prices.
I used all my fiat and bought back in, less than 1 minute before that happened. god dammit. It was fluctuating between the 100s and 400-500s back and forth for a good 10 seconds before it finished/corrected. I could have probably snuck in a $300 order if i had the fiat.