Quelques précisions sur la redirection USB RemoteFX cf http://blogs.msdn.com/b/rds/archive/2010/11/08/introducing-microsoft-remotefx-usb-redirection-part-3.aspx

What are the requirements for RemoteFX USB redirection?

• RemoteFX USB redirection is only available when connecting to a RemoteFX-enabled Windows 7 SP1 virtual machine (VM) running on a RemoteFX-enabled Remote Desktop Virtualization Host server. For information about the requirements for RemoteFX, see Beta testing RemoteFX in Service Pack 1.
• RemoteFX USB redirection is not available for connections to a Remote Desktop Session Host server.
• RemoteFX USB redirection is available for connections to VMs through RD Web Access and for RemoteApp programs running on RemoteFX-enabled Windows 7 SP1 VMs.
• The Remote Desktop Protocol (RDP) 7.1 client must be installed, and the Group Policy setting enabled. See Part 1 of the blog. You must restart your client computer for RemoteFX USB redirection to be functional.
• The USB devices that you would like to use in the remote session must be plugged in before starting Remote Desktop Connection; devices plugged in during the session will not be redirected.
• RemoteFX USB redirection, like the rest of RemoteFX, has been designed for LAN connections (< 20 ms latency); on the WAN, some USB devices may not function properly, or the user experience may not suitable.
• Due to USB limitations, a device redirected by using RemoteFX USB redirection can only be used in one RDP session at a time, and cannot be used locally while it is redirected to the VM.
• If you add a new device to the client computer that you want to redirect, you must log off from your virtual desktop and then log back on.
• Drivers for redirected USB devices will be installed on the VM by using the same process that a physical Windows computer uses when a device is plugged in. Please ensure that Windows Update is enabled on the VM or that drivers are available for the device in question.