I am recently unable to record on any existing or new audio track in any Sonar project.  When I try to record (R), I can see the input level in the track view bouncing back and forth as it should, when I play before or during recording.  So there is no question that the track is receiving my audio signal. But the resulting audio clip just shows a flat line, as if Sonar is ignoring the audio signal it receives. I have the track armed, and the audio punch toggled off.  I tried creating a new audio track in a new project, but the same thing happens, I can see the input signal, but the clip is empty.  AFAIK, my audio track's input and output settings (and all project settings) haven't changed since I was last able to record.

I don't see audio signals in my Xonar Audio Center when I play or record, though I've seen audio signals there
before. But since I see the input signals in my Sonar audio track ok, it doesn't seem to be a sound card problem.
Any ideas? 

Sonar X2

HP Z210 CMT
  3.3GHz
  6 GB RAM
  Xeon E3-1240 Quad core
  Windows 7 Professional 64 bit

Xonar Essence STX sound card
Sample Rate: PCM 192 KHz
ASUS driver
Audio Channel: 2 Channels

Audio Track:
Input:  Left Xonar Essence STX ASIO(64) IN-00
Output: To Xonar Essence STX ASIO(64) L

Am I reading this right, your trying to record at 192 with a $10 sound chip??

Please confirm:
Have you auditioned if anything gets recorded or not? The flat line in the clip may just tell your picture cache is full.
The waveform in the clip is just an independent picture, it's not "tied" to the existence of the actual audio file.

Yes, I've listened to the clip, and there's no sound, no matter how high the volume.
 

Hello,
Does opening project show you a 'output is assigned to silent output'. I've had this happen before, but it's been awhile. Is recording set up to show wave files while recording. If so, does the wave show sound being recorded. If it does than sound should be there. Could be routing problem. I've noticed that Sonar sometimes does what it wants to do.
MJ

Cactus Music
Am I reading this right, your trying to record at 192 with a $10 sound chip??

A little unfair as it is not a $10 Sound chip did you check out the sound card.
https://www.asus.com/Essence-Hi-Fi-Audio/Xonar_Essence_STX/
More a $130 sound card.

Gordon check that your sound card is also selected as the device to use in Windows Sound devices.  I have had a situation where my PreSonus USB Audio Box was not selected as the device to use in windows result was silence.

Also, do you have some other software program open that might be stealing control of the driver?

Sorry, I just assumed it was an on board audio chip, But still it's a Gaming card and we've all been down that road before. Pretty rare that good ASIO stable drivers come with those type of cards. The real deal PCIe cards are 6x that price point.    And I'm wondering if the issues would go away if the OP tried a more reasonable sample rate like 48. 

Apparently its for headphones and is not a game card.  I know of no game that uses ASIO.

It appears to be for enhancing the listening experience of everything, Games, Movies and a lot of good stuff, but it was not designed with DAW recording in mind, nowhere is this mentioned in the user guide. It should work but to me it's like the negative experience I had with my Creative Audigy card which is in the same category as this one.   
It does not mention ASIO drivers anywhere in the manual, but I see from the OP's  list that it must use them. 
 
So I would say try a more reasonable sample rate even 44.1 and see what happens first. 
But the probability that the drivers are not going to play well with Sonar is high as we see all the time when people try using none trusted brand audio interfaces round here. Sonar is picky about drivers.