It drives me crazy!! I can record, see the preview waveform but when I hit stop, or even pause (tried to be smarter than X2), it is gone! There is not any sound recorded.
I tried all the stuff in the forum to solve my problem, without any results. See for example http://forum.cakewalk.com/FindPost/1892872 and  http://forum.cakewalk.com/FindPost/2819316
 
I have this problem in X1 and X2, but not in 8.5.3.
So for the moment I record in 8.5.3, the only way for me to work around. 
 
Can somebody help me?

With a fresh test project started, but before inserting an audio track or arming it to record, open Explorer views of the audio folder and the picture cache and arrange SONAR and the two folders so you can see all three.
 
Watch the audio folder as you insert and arm a track, and you should see a file created with a name like <Project Name> Rec (1).wav that is on the order of 4kb in size. If you start recording, and continually refresh the folder view, you should see that file grow steadily. When you stop recording, the file will be renamed to include the track name, and the number will increment so you have a file named like <Project Name>, Track 1, Rec (2).wav. You should also see corresponding .WOT and .WOV files appear in the picture cache at this point.
 
Try this, and let us know how much of that is happening.
 
 

Brundlefly, that was a very good idea and there was a weird action!
I created a new project and in the audio folder I saw 12 files: .....,Rec (1) to ,Rec (12).
In the picture cache there was a file 7A10.tmp .
 
Then I started recording, during the recording nothing changed in both folders, even with F5 refresh.
But, when I stopped recording, there was a new file in the audio folder ..., Rec (13).wav and in the picture folder two new files ...WTR and ...WOV.
And...(of course) the wave was in X2 and I could still hear it during playback!
 
So, everything is normal, but what is wrong with my project?
I made it in 8.5.3 and migrated to X2 to work further with it, including recording new voices. Every change or new sound (midi/instruments) works fine, but no audio recording. I watched both the folders from my project when I tried to record now in my own project.
Before recording, track armed, there were 5 files in the audio folder: ...,Rec (3534) to ..., Rec (3538), each 4 kB, and in the picture cache one file 12.tmp (empty).
During recording the wave was nice pictured in X2. After stopping the recording the wave was gone again as usual, and in the audio folder the 5 files were replaced by new files, also each 4kB and with names ..., Rec (3539) to ..., Rec (3543).wav
In the picture cache after disabling recording knob, the picture file was gone.
 
So I am really wondering what is happening here.
 
 

Obviously something didn't translate when opening that project in X2, but I haven't run into this with any of my old projects. I would check/try:
 
1. The sample rate of the interface hasn't changed.
2. The Record Bit Depth in Preferences > File > Audio Data for recording in SONAR hasn't changed
3. The default sample rate for new projects in Preferences > Audio > Driver Settings agrees with the project sample rate (shouldn't matter but can).
4. Change the inputs on audio tracks to some other channel and back to be sure they are set correctly "under the hood"
5. Try creating a new track and recording to that.
6. Contact Cakewalk Tech Support.
7. If all else fails, create a new project from scratch in X2, and import as much of the old one into it as you can and replicate other settings manually as necessary.
 
 

Brundlefly, thanks for your patience.. I noticed thanks to your suggestions, that some tracks in the project have 32 bit depth, but most tracks have 24 bit, the standard for me in my options. Sonar 8.5.3/X1/X2 have all the same options in samplerate, Record bit depth and audio driver bit depth (64 bit double precision). Could that cause problems, if you have in your project 'mixed' audio tracks from 24 and 32 bit depth?
 
I tried another old projcet I made in 8.5.3 - which had only 32 bit audio tracks - and added a new audio track 24 bit in X2. I could record and there was a wave after that! So maybe it is a matter of different bit depths? Though I could record in 24 bit with older audio tracks in 32 bit.
 
Tomorrow I will do your other suggestions.
 
I contacted Cakewalk Support, mentioned the problem with recording audio in X1/X2 but not in 8.5.3, but the answer is only for X2 (check audio card and reinstall X2), so I will send them the new found information about recording in a new project that works well in X1/X2.

This has to be said.
 
Dave (Brundlefly) has never been flashy. He is quiet and unassuming. I have never seen him bash anyone or cause any conflict. What he has done through all these years is post some of the very best posts of anyone and answer questions brilliantly. He does this over and over again. Here in a highly creative way he has out done himself and provided a recipe for the OP that is both insightful and brilliant. Yet its offered in a manner of fact way that belies the great mind behind it. Very typical of him.
 
We his fellow forum members are blessed by him being on this forum.
 
Thank you Dave.    

Mixed file bit depths shouldn't be a problem. Really none of the things I mentioned should be a problem, except for having the interface's clock rate match the project. But in the context of bringing old projects into a newer version, anything's possible.
 
Also, I haven't done done a search, but I meant to mention that this problem has been reported in the past, and there may be a solution buried in the archives somewhere. I'll take a look.
 
Try this post/thread, for example:
 
http://forum.cakewalk.com/FindPost/1982639
 
This one looks promising, too (disabling Allow arm changes, although it shouldn't be a problem):
 
http://forum.cakewalk.com/FindPost/2766135
 

John
We his fellow forum members are blessed by him being on this forum.
 
Thank you Dave.    

What can I say but thanks, John, and you're welcome. I wish my day job customers appreciated me as much.
 
Now I await responses from the half-dozen members I have bashed along the way. 
 
 

John
This has to be said.
 
Dave (Brundlefly) has never been flashy. He is quiet and unassuming. I have never seen him bash anyone or cause any conflict. What he has done through all these years is post some of the very best posts of anyone and answer questions brilliantly. He does this over and over again. Here in a highly creative way he has out done himself and provided a recipe for the OP that is both insightful and brilliant. Yet its offered in a manner of fact way that belies the great mind behind it. Very typical of him.
 
We his fellow forum members are blessed by him being on this forum.
 
Thank you Dave.    

I'm with you there, John, 100%.
 
If I see Brundlefly has posted, I always make a point of reading his posts.  I enjoy his calm, knowledgeable and, as you say, unassuming manner.
 

This one looks promising, too (disabling Allow arm changes, although it shouldn't be a problem):
 
http://forum.cakewalk.com/FindPost/2766135
 
Dave, that was the golden tip! By unchecking this option, the wave is there after recording.
So thanks a lot for your help, I am a lucky man now.