I'm evaluating USB Redirect feature because our core business app needs to recognize the USB device as local device. Once I installed "usbrdp_ce500_x86.CAB" into my HP thin client, it works for a while, but then it shows "Unidentified USB Device" message on WinCE (not RDP session), all usb devices stop working including keyboard and mouse. After I reboot the machine, keyboard and mouse were still not working. I had to restore thin client to factory default setting in order to get mouse and keyboard to work, and I also noticed that the installed "USB RDP" program was gone after I restored.
HP Thin Client t5520 CPU: VIA Eden ESP 800MHz OS: WinCE 5.00
After you have restored you Thin Client please try installing the "usbrdp_ce500_x86.exe" (not cab) int different (not default) folder (Mike Storm has provided you with exe installer)
After the installation turn off the "auto-redirecting" option ( To do it press "settings button" in USB for Remote Desktop workstation CE window)