Windows Server 2008 R2 STD doesn't accept first attempt to RDP

I have a terminal server running Windows Server 2008 R2 Standard and there is strange issue that I cannot connect to the server via RDP when I try to do this for the first time, but after first attempt fails, and I try one more time - session can be established and runs smoothly.

There were errors in event viewer like these:

EventID 56 description:

The Terminal Server security layer detected an error in the protocol stream and has disconnected the client. Client IP: www.xxx.yyy.zzz 

EventID 50 description:

The RDP protocol component X.224 detected an error in the protocol stream and has disconnected the client.

which were fixed by disabling some of the advanced features for TCP, described here.

The server is virtual vmware server and not joined to the domain. Has anybody experienced something like this? Any ideas what maybe wrong?

UPD1: I also tried to change RDP-Tcp settings in Remote Desktop Session Host Configuration console on Network Adapters tab specifying exact adapter to use, but this had no effect.

Solution 1:

Finally, I've been able to resolve this after a couple of days.

This is what have been done to fix it:

Step I:

Added a new DWORD key named DisableTaskOffload with a value of 1 to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Step II:

Changed IPv4 Checksum Offload for PROD NIC in Advanced Settings.

After these changes, no more issues with RDP not been connected at first attempt or performance issues.