Just keeping everyone informed, CityIndex closed out my short position on the Dell Sept contract today claiming that I had fallen below the 80% margin level. I checked the chart and sure enough there is a spike in Dell's price. On further investigation this spike does not occur on any other platform. Also, to add insult to injury, CityIndex did not even do me the courtesy of giving me a margin call. This is the first time I have had to deal with such unprofessional behaviour and I just thought I would warn people to keep a close eye on their accounts with this crowd. I have uploaded 3 charts below (one from Yahoo site, Igindex and CityIndex ) to illustrate the discrepancy in pricing.