You might also want to check your duplex settings. Normally GigE should be set to full duplex on both sides, and not to autonegotiate.

One of the most common findings when a Ethernet connection is losing packets or is just slow, is that one side or the other was set to autonegotiate and wound up in half duplex. If both sides start to transmit at about the same time, the half duplex side will see a collision, transmit a jamming signal, and assume that the other side is going to back off and retransmit... but the full duplex side is not looking for collisions and will never retransmit.