As I stated, the MC help it says to send it to JRiver, but I cannot find any way to contact them to request support.
JimH, the person you've been talking to, is the CEO of JRiver. You've contacted them.
When MC crashes it keeps playing music but it will not respond. In fact no program other will respond either and Windows will not respond. I cannot bring up the Task Manager. I cannot kill any program or process. I cannot switch program. I cannot even reboot.
Windows does not give Media Center, as a user-space application, the capability to do that to your computer.
What this means is that a hardware fault has occurred or a driver has crashed.Drivers can do that, but MC cannot. MC can only use the drivers, and they're supposed to do what they're supposed to do. Yours are not for some reason.
It is possible the driver you have installed for some device on your computer is buggy. This is most likely the audio device, since using the audio device triggers the problem. Here are some resources you can use to track down drivers for many common components:
http://wiki.jriver.com/index.php/Troubleshooting_DriversIt is also possible that there is something physically wrong with your computer. This could be one of a variety of components failing or overheating. Again, however, if using the Audio device for playback triggers it, then I'd look there first.
Lastly, it is possible that you have malware installed on your computer that is operating inside the kernel of Windows, and is crashing or locking you out of the computer. This is probably the least likely of the three scenarios I mentioned, but worth bringing up.