It’s a bad thing that Sonar is crashing on you as often as your matter of fact explanation seemed to indicate.
The best option is to reboot.  You have an i7 so rebooting shouldn’t take that long.
I suggest you ought to drill deeper to find out what is causing this. One option is to go into the Computer Management console of Win7 and look into the Event Viewer Log. You should see Application Fail log with sonarpdr.exe as the error. On that page which comes up it may show more indication as to what caused Sonar to fail.
In my case for example it showed a freebie vst plug I was using as the faulting module.
Quick way to get into computer manage is:
Right click on (My)Computer.
Left click on Manage. You will see on the left pane the Event Viewer page.
Launch Application logs. On the right you can find the Red Error with sonarpdr.exe.
I am on Vista but I think this procedure is the same or similar to Win7.  

Another approach is to use Process Explorer from sysinternals instead of the Task Manager to kill sonarpdr.exe. Process Explorer has, in addition to "Kill Process", a "Kill Process Tree" function that kills all child processes first before killing the main executable. This will sometimes allow you to end a "stuck" process that Task Manager can't halt.

The exception is when you have a hardware or driver problem that causes SONAR to sit on a queue waiting for something to happen with the hardware that isn't going to happen for whatever reason. Process Explorer can't help you with that. For that, you have to disable the device or reboot.

WillInIll


I guess, what I was getting at was, is there some feature, in the OS perhaps, that would allow me to uber-KILL a process that doesn't want to end? I run it as admin already. Can't think of anything else. I figured "end process" means "end process", but with Sonar, it means something else.

You run what as an admin? Sonar or software from your interface? Only Sonar should be run as an admin.

Couldn't find another more recent thread, but thought I'd add a hint in case others have this problem too.
 
I have this problem from time to time and my setup has a USB midi keyboard controller and internal sound-card. Turning off or unplugging the keyboard does not help.
 
What does help is going to the Windows device manager and finding the sound card then choosing "disable." The sonar.exe process will disappear from the Task Manager, and then choose "enable" back in the device manager for the sound card that was just disabled. Restart sonar and all is well again.... no need to restart computer.