Really good to read this and to know about precedence set in order to make the same mistake.  I tend to save files in bundled formats and it never occurred to me that could potentially corrupt the file.  Seems like this would show up on the Sonar radar.  I've got Sonar 7 and will not try this at home...or in the studio, in this case.  I've been curious about how reliable cloud storage is for the same reason.  What if????  Can never have enough back ups.

When you make a bun file, always check it right after to see if it can be opened before deleting anything. And don't rely on it as the only means of back up.

I had always saved as Bunfiles.
With this particular project  I saved Bunfile to my C drive.
I saved Bunfile to one of my external drives
I saved Bunfile to clients drive.
All project folders and data deleted from C Drive as we thought 3 copies of the Bundles
would be plenty safe backup. El-Wrongo
 
As a PAID REGISTERED Sonar customer, I still have not heard a peep back from Sonar Tech.
Great customer service eh?
 
So if nothing else, I hope others read this and use other methods like copying their Per Project Folders
to another drive and DO NOT USE BUNFILES.

You've been asked (and I just did in your other post on this same matter) to confirm if all the three bundles you saved have gotten corrupted. You have not clearly stated that yet, as far as I've noticed. That would be just more than bad luck, unless you have created two copies of the one original bundle instead of saving three times as a bundle file.
 

BoostSoftware
Really good to read this and to know about precedence set in order to make the same mistake.  I tend to save files in bundled formats and it never occurred to me that could potentially corrupt the file.  

Any complicated file can get corrupted somehow. Saving as a bundle does not corrupt the file per se, as mentioned several times, and bundle is a very good format for web co-operation of music makers. It's just that IF it gets corrupted, you can't do anything ( unless the software mentioned in these two threads can do something).
 
It could be considered strange that CW doesn't have a de-bundling software in its arsenal.
 

from the cakewalk knowledge base-

Tips on Backing Up - Bundle Files

Backing up your Cakewalk files - The benefits of the Bundle
In the wonderful world of computers, backing up your work is more than a good idea. It's essential when you're using your computer for creative projects. Making backup copies of your Cakewalk files is quick, easy, and can save you some serious headaches, as well as hard drive space.
The preferred method for backing up files containing audio data is to save them as Cakewalk Bundle (.BUN) files. Here's how to do it in Cakewalk:

1. Choose File | Save As.
2. Change the Save As Type to Cakewalk Bundle.
3. Name the file.
4. Choose your saving location, and save the file.

Why use Bundle (.BUN) files rather than Project (.WRK) files for backing up?
First, a quick lesson: A Project (.WRK) file contains MIDI data, project-specific settings, and references to audio data that resides in the location specified by the current Data Directory (Options | Audio | Advanced). Backing up the .WRK file, or transferring the .WRK file from one machine to another, will NOT automatically backup or transfer the audio clip files referenced by that .WRK file. So saving or copying a .WRK file alone is not enough to safeguard your projects or transfer them to a different computer. 
The .WRK format is perfect for everyday Cakewalk use, and we don't suggest you save as a Bundle every time you save. However, once you've come to a point in a project where you've made significant progress and feel the need to back up the file, the Cakewalk Bundle comes into play.
The Bundle (.BUN) format preserves ALL data, audio and otherwise, in one file, which can then be moved to any location you like. Because of this, these files also tend to be quite large and slow to open. You'll need to save your Bundle files on your hard drive, or on some large capacity storage medium such as a CD or tape drive. Once that's done, you can delete the .WRK file version, then use the Clean Audio Disk command to remove the associated audio files (which you don't need because they're saved in the .BUN file now). This will free up space on your hard drive for your next project.
When you're ready to work with the project again, simply choose File | Open and navigate to the location of the Bundle file. The file will open with all data preserved just as you left it.

Yes. That's rather blunt :o/
CW really needs to pay a little attention to this.

The above information refers to .wrk and .bun files.

What was the last Cakewalk Program to create those files. Certainly not the Sonar range.

If I was to have read that document as a resource I'd be questioning what those file formats have to do with Sonar.

All this talk about the failure of cwb files is a beat up. They are no more prone to corruption than any other file form. File corruption due to hard drive speed is pretty speculative and not supported by any evidence that I've been able to find.

The fact is that any file format can become corrupt. EVEn if I use a zip program to bundle some files I'll test it straight away to make sure that it decompressed properly. The same with Cakewalk bundle files.i know it terrible to lose work. Been there done too and it can be very expensive to recover data if that's even an option. A proper backup scheme is what's really required.

Cakewalk are usually very helpful with sorting out corrupt file problems.

mudgel
The above information refers to .wrk and .bun files.

What was the last Cakewalk Program to create those files. Certainly not the Sonar range.

CWPA9 (Cakewalk pro audio 9) was the last to use .wrk but .wrk was used in cpw30 which came on 1 floppy disk.
.cwp began with Sonar 1 which came directly after cwpa9,
and I had been hearing about bun nightmares since Cakewalk 5
so who knows how long that knowledge base article has been there.

never did a bun and never will

I think the whole point of this thread is the OP was told with the upmost authority by Cakewalk  that using CWB ,BUN files was by far the best choice for back up. 
Sure all files formats can be corrupted, But there is no way to retrieve your audio data from a corrupted CWB file. There is from a corrupted CWP file. 
 
The Cakewalk data base needs to sorely be updated. 
 
It should also say 
We recommend you back up your work regularly. You can use CWB files but be warned all data will be lost if they are corrupted. So as a precaution please also back up using a combination of CWP and MIDI files as well.  

i would be a happy camper right now if there was a way to extract just the audio files from a corrupted bundle.  can't someone at Cakewalk (or anyone else, for that matter) invent a utility for corrupted bundles????