I have two separate IB accounts and this problem has happened in both accts. today at different times. When I tried to place an NQ order, I got the error message: "Your order is not accepted. In order to obtain the desired position your NET LIQ in USD denominated assets must exceed the margin req. for those assets." I contacted the help desk and the 1st time it happened the problem resolved itself in about 5-10 minutes before the chat guy could help. Contacting them again now. I have plenty of cash on hand to cover the margin...anyone else have this problem? I'm not happy, needless to say. When I placed a T-Bond order it would accept it, but not an NQ order.
IB's reply was that their programmers were aware of this issue and they hope to get it fixed by tomorrow.
I have had the same case (I dont know the error message exactly) . The automated generated order through the API for ES was sent out - but the NQ order was rejected.