I was saving a project and Sonar X3 Producer crashed before the save was completed.  I restarted and tried to load but get this message:
 
"Could not open this project because the file has been truncated.  This can happen if the application closed unexpectedly while saving the file."
 
Not helpful.  I tried opening it in safe mode and get a blank file even though the file size is 2,515kb.  There is a file with the extension of .assets from the same time of the crash but it is only 1kb.  Am I doomed to have to redo my work?  Is it lost??? :( :( :(

If you can't see a file named "Auto-save Copy of ... .cwp" so you lose your file maybe.
You must go to Edit | Preferences | File | Advanced , and there you can activate autosave and tell to Sonar when it autosaves , for example after 2 minutes or after 10 changes ...

Any recorded audio is still salvageable in your audio folder.

I guess by default the auto save wasn't on.   I don't have a recording because the problem was a stuck note that I had fixed.  That stuck note was in the audio and rendered the mix down useless.  So I have 2.5 megs of the file and because it doesn't have an end, I lose everything for the past week?  That's amazingly disappointing considering Sonar crashes daily.  I thought the auto backup would kick in when the program crashes during a save.  So I have no options?  Isn't there a way to open it and just lose the last set of changes???  I want to throw the computer and Sonar out the window right now.

Having been burned by computer glitches and software hangs over the years I've developed a behavior of creating a Save As trail of versions of files I'm working on. So for every song I start with something like "Song Name" PL15E rev1a. 20 mins or whatever series of changes later I use Save As and continue the work in rev1b, and so forth.

I'm happy to trash 20 Save As versions when I am further along. It's easy to trash. It's not easy to reconstruct or re-perform stuff, or remember the creative ideas, if saving in only one file and it gets messed for some reason.

I happen to append PL15E to note what version of Sonar I'm using while working on the piece. As time goes on it's been useful for me to know which exact version of Sonar I was in when returning to the file at a later date or for rework.

15 is this year, E is Everett at the brief moment...

I think you can just activate autosave to prevent from future losts :)

Did you save your projects as per Project audio folders.
Then your audio is in the audio folder within your project folder. If not then you should certainly start that habit along with setting auto save.

If not per project audio then check in Sonar's file locations where your default audio folder is. That's where the audio from your project will be. Did you have audio? If it's all MIDI I'm afraid you're sunk.

Got to learn good backup habits for just this case. Computers vacant be relied on to always do the right thing.

It is all midi so it sounds like all original work is lost.  Sonar x2 seemed to at least attempt a dump save if the app crashes during a save but X3 seemed to either not do that or have it turned off by default.  I am heart broken to say the least. 

karelm
I guess by default the auto save wasn't on.   I don't have a recording because the problem was a stuck note that I had fixed.  That stuck note was in the audio and rendered the mix down useless.  So I have 2.5 megs of the file and because it doesn't have an end, I lose everything for the past week? 

Sorry for your pain. I've experienced a HDD crash, and I know how it feels, when you don't have backups fresh enough. I lost a years works (not as much as it may sound, though) and learned my lesson.
When you actively work on a project, proceeding a lot every day, you should do a backup copy every day.
When the program crashes, it's too late for any auto-save  to do anything.  

Reiterating. I think saving out Save As files (versions) is more convenient, wise, and practical than relying on AutoSave - I have both in my method. True, AutoSave might have a useable version from 10 mins ago if you hang. That can save a step to get back to where you were just working.

Prior Save As versions are great because you can go two hours down the road on a song and realize where you were 2 hours ago was better than where you are presently at with your creation. It allows you to quickly restore from any point (any saved version) you need. In addition, AutoSave versions may also have had a glitch. I've found on a variety of crashes that the AutoSave file was truncated or wouldn't load. Easy enough, I could just load a previous Save As version.