If you are flummoxed by the relationship between pre-market moves and market action when the market opens, then you are not alone.
The movement in the e-mini futures has been volatile in the last half hour of trading, after the market closes and before the market opens. Given the lack of liquidity in the equity markets right now, it does not take a huge amount of trading in the e-minis to move the markets in a dramatic fashion.
The problem is that the futures markets are regulated by the CFTC and stock markets are regulated by the SEC. Both are failing to take action as this problem gets more virulent. Something needs to be done by either of these regulatory organizations or our legislators to restore order to the markets. If you want to understand index futures in greater detail I suggest you read an article that I wrote for The Street.com (TSCM) last year titled Five Things You Should Know About Index Futures .