Creenome, i experienced this issue and i dont know what the problem is exactly. what i do is just use small orders with small time delay. mostly if i use margin i market buy or sell anyway and dont put limit orders. so if i have 10 btc to play, i would fire 2 btc each 3 secounds or so directlys into the bids/asks. with that you are at least able to enter quickly with the majority of your money when there is movement in the market. becasue polo can lagg too, and when after 20 sec of lagg this message pops up (instead of "margin order placed" or whatever, its really frustrating.

What do you think is a good price to buy?