I placed a limit order to buy shares of an AMEX listed security. I got a partial execution which was followed by a rise in the stock price. I left the unfilled portion of the buy order alone and tried to place a sell order (a limit order at the bid price) for the position I now had. The order was hung up and I thought it was a technical problem. After some research, my broker told me that there was a restriction at AMEX on having simultaneous buy and sell orders for the same stock. I don't believe this same restriction exists at NYSE. Anyone familiar with this?