EthernetClient.cpp in 1.5.x has old pre-1.0 flush() function that discards input. Arduino 1.0 changed flush() to complete transmission.

https://github.com/arduino/Arduino/blob/ide-1.5.x/libraries/Ethernet/src/EthernetClient.cpp#L122

void EthernetClient::flush() {
while (available())
read();
}