I know this is an older topic, but perhaps my hint will help folks who have the same question.
As far as I know, the Media Center Extender interface (not the MediaLounge interface) uses the same remote control signals as a standard Microsoft Media Center remote control. So, if you have problems configuring your Logitech remote to control the DSM-750, pretend the DSM-750 is just a Vista Media Center PC. This will load the correct codes into the remote.