I don't think it's a Vista 64 bit issue, since Matt is using that OS here and it works fine with various remote transceivers. KingStyles has two MCE type remote receiver devices and that may be the problem. I'll do testing here with two devices and see if I can duplicate the problem and fix it. Mr. Chriz has a different issue, none of the remote plugins are showing up in Media Center.
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Mr. Chriz, what do you see when you click the "Devices & Options" link and then view the "Selected input devices" drop down? On my system and KingStyles' a "Microsoft MCE" device is checked and also "Remote, gamepad, or other HID".
Also, do you have two remote transceivers on your system like KingStyles?