I've been daytrading on and off for several years and just ran into something I've never seen before. I use Tradestation as my broker. I bought a position in TQQQ yesterday; held it for less than 1 hr and sold for a profit. I then proceeded to trade numerous stocks the rest of the day. I seldom hold anything overnight. This morning I was unable to place any opening orders so I called TS. They said I had triggered a daytrading margin call. My account has about 65k in it so not an issue w/ the PDT rule limitations. According to the agent, TQQQ has a higher margin requirement which is understandable but I was still allowed to buy a number of shares that put me over the limit and then get a margin call triggering either a 90 day restriction or adding extra funds all for a trade that I closed the same day. Am I missing something here? I can't believe I would have never triggered this before. The platform obviously wont allow me to outbuy my buying power; why did it allow me to outbuy the margin requirements on this stock?