Hangs at "Initiating Remote Connection" using RD Client 6.3.9600

Hi All,

I have the following setup, all in 2012 R2:

2x Gateway

1x Broker/Session Host

1x Session Host 

When I connect to the broker through the gateway, everything works if the session host is the broker/session host, but if the session is redirected to the non-broker host, it hangs at "Initiating Remote Connection" indefinitely. It works fine with previous versions of the RD Client, and works fine from the MS RD Client for OSX. I see the following warning in the event logs on the client side:

[ Name]  Microsoft-Windows-TerminalServices-ClientActiveXCore 
 [ Guid]  {28AA95BB-D444-4719-A36F-40462168127E} 
   EventID 226 

RDPClient_TCP: An error was encountered when transitioning from TcpStateConnectingTransport to TcpStateDisconnected in response to 2 (error code 0x80004004).

Has anyone seen this behavior before? Anyone know a workaround aside from using an older client? 

Thanks,

-Dan