When I try to connect to the Windows Server 2008 SP 2, the connection is immediately disconnected with an "internal license error". Maybe this is part of the lacking RDP 6 support in rdesktop? If I remeber correctly, this worked well with the pre-SP2 version of Windows Server 2008.
Ok, I just resolved the issue. It seems that rdesktop had stored an invalid license file in ~/.rdesktop/license*. It worked well after removing that file. See also: https://sourceforge.net/tracker/?func=detail&aid=2211171&group_id=24366&atid=381347
This only solves the issue temporarily for me. On next reconnect I get the same error again and have to wipe the license file again. Also it's not possible to drop back to RDPv4 as then the error is:
ERROR: channel_register
WARNING: Initializing sound-support failed!
X Error of failed request: BadAtom (invalid Atom parameter)
Major opcode of failed request: 23 (X_GetSelectionOwner)
Atom id in failed request: 0x0
Serial number of failed request: 55
Current serial number in output stream: 55