Any other ideas?
Lots.
First, as you had MC20 installed, and have now uninstalled it. Do a clean reboot of your HTPC, then reinstall MC21 over the top of the existing MC21 installation, reboot, and test again. Make sure that you allow any MC related processes if your antivirus or firewall software tries to block anything. In fact, make sure that both your antivirus and firewall are not set to automatic or silent mode, and are set to ask what to do if they see something they want to block. You can change those settings back once the problem is resolved. If that doesn't work, then ...
I was going to suggest starting your HTPC in Windows Safe Mode, then running MC21 and seeing if the remote works. If it does, then something else on your HTPC is capturing the IR commands, interfering with the driver, or similar. You could still try that, but the driver for the IR device may not load in Safe Mode. . .
Actually you should be able to check if the IR device appears in the Device Manager after you have restarted in Safe Mode, and if it has, it should work in MC21. If it does not, Google remote control testing software to find something that will detect IR commands and show you they are being received. Perhaps something as simple as
WinLIRC would be enough. Perhaps install and learn how to use that before going into Safe Mode. If you can confirm that IR commands are being received using WinLIRC, and yet MC21 is not receiving them even in Safe Mode, then it could be that there is something wrong in MC21.
If Safe Mode just doesn't allow the use of IR, then try using msconfig.exe to turn off everything that should not be required on the Services and Startup tabs, then reboot to that configuration and see if the IR device is in Device Manager, as it should be, and then test if the remote works in MC21. Using msconfig can be a little fiddly though, as it is pretty hard to work out what is essential and what is not. Basically I turn everything off that I possibly can, leaving Microsoft services running, then reboot and see if anything is missing, if so, back into msconfig and turn it on, etc. until I get a working environment with the minimum features, and
then I test whatever it is that needs testing. In this case, the remote in MC21.
Basically, I am assuming that something is interfering with MC21 receiving the remote commands. Maybe MC20 Server, antivirus, firewall, maybe something else.
Vocalpoint and Gappie, the Next button at the bottom is just the first step in setting up MC to control other equipment using an IR blaster, as described at the top of the Remote Control dialogue. If you aren't trying to do that, then don't be concerned that it doesn't work. MC may be detecting that you don't have an IR blaster, although the message is a little ambiguous. Maybe even incorrect. Interestingly, I don't get that message, and I don't have an IR Blaster. But I am using an internal CIR, which is probably reporting that it has a blaster, as it has the capabilitiy.
Anyway, if "Microsoft MCE" is Active under "Devices & Options", then I believe that MC knows you have a working IR Receiver.
Vocalpoint, perhaps you could use some of the information above to track down your JRemote vs Remote control issue. At a minimum, check that the IR Receiver is still present in Device Manager whenever the remote stops working.