No probs with CWB's here. Been using them since the X series but I also export the individual .WAV files as yet another back up and safety measure to be on the safe side. I also back up to 3 different places. Internal drive dedicated for back ups, External drive and DVD. I'm not paranoid. Lol.

I back up ALL the time to a bundle.  I've yet to have any issues unpacking.  Ever!

"Digital data is not real unless it exists in at least two places"
 
Those used to be my "words to live by," but now it's two hard drives, a Blu-Ray or DVD optical disc, and a separate backup for all three that consists only of rendered WAV files so they can be brought into any project.
 
For really important projects, on-site backup is important as well. The cloud is good for this.
 
Bundle files existed before Sonar offered the per-project saving option, which is waaaaaay better than the days of dumping all the audio in a single folder and having projects point to that audio. Technology has changed a lot since the bundle file was introduced. I don't use bundle files, but not because I've had problems with them; I haven't. It just doesn't seem optimal to save everything in one huge file where if one bit is missing, you're hosed. I've downloaded plenty of zip files from the net that won't open because they became corrupted during the transfer, which seems like the one-size-fits-all file format is trying to tell me something...

OK, Ok we know there are plenty of people who have used Bun file without issue, that has never not been clearly understood here..  But that does not help the folks who do have issues.
What would be nice is a clear understanding of what goes wrong, and under what circumstances. Obviously something goes wrong in the creation of the file otherwise the dude who has 3 backups would not have all 3 corrupted.
There also seems to be the understanding that it goes wrong a lot more that it does with CWP files. I guess we will never know that answer without polling 1,000 users. 
 
it would be good to hear from someone who managed to salvage a file. 

What I'd also like to know is whether anyone who saved a bundle filed opened it immediately after saving to see if it loaded properly or not. If not, then it would seem like a good idea to save using a different format. If so, then what about a bundle file "aging" would cause it to become corrupt over time? I know hard drives block off bad sectors, and sectors can go bad over time...could that be part of it? Do bundles saved to flash drives fare any better? What about optical drives?
 
FWIW whenever I save something with any program I always try loading it before shutting down the program, just to make sure.
 
We have plenty of anecdotal evidence that some people have problems with bundle files, but the circumstances under which any problems happen haven't been very explicit...they generally go along the lines of "I saved a bundle file years ago, I tried to open it recently, it doesn't open." Some more data might help narrow down a possible failure mode.

If Sonar stores a checksum in somewhere in the file Sonar should diagnose these sort of issues straight away Craig... I have no idea whether this happens or not.

I never have issues, I wonder if it is peoples antivirus that's doing something to it such as locking a file. The other issue is how well bundles work from earlier versions of Sonar.

I'd be keen to find out if people have any issues with brand new projects created with X3.

I guess the problem is those who have been having issues never get back to the forum with any follow up, I dug through a bunch of threads on the topic and every single one had the same ending, the regulars asking more questions and the OP disappears into the ozone. 
That is one reason I started this thread. So we are still waiting to hear back from anyone who figured this mystery out. 
 
My feeling is this is not a case of anything going wrong with a hard drive or whatever, It seems to point at the files might just be corrupted the instant they were created. 
The other unanswered question is whether this is a change in audio format issue. After all the message they get is the audio is corrupted. Or is it a change in OS, or a change in Sonar version, 32 bit or 64 bit???? 
 
And is Cakewalk going to keep that outdated knowledge base article recommending bundles I copied to my opening post? I will certainly continue to advise not to use them without a CWP backup alternative. . 

And I'm still waiting to find out if anyone opened their bundle file after saving it to see if it opened correctly.

On the occasions when I've used bundle files, I've always treated them like any archiving software. ie create the bundle and before moving or sending it somewhere I ALWAYS open it to check the archiving process worked properly. If it checks out OK then I can use it if not on the occasion is where there's been a problem usually doing it again has resolved whatever the original failure was. Have to admit I've had that occur probably as frequently as any archiving attempts with zip, rar or other earlier windows archiving utilities. That means occasionally I've had a failure. The advantage of zip and rar archives is that there are utilities available that let you examine the archive and often you can salvage many of the files

mudgel
On the occasions when I've used bundle files, I've always treated them like any archiving software. ie create the bundle and before moving or sending it somewhere I ALWAYS open it to check the archiving process worked properly.

Absolutely this. I can't imagine why anyone wouldn't. I also wouldn't keep any kind of compressed/zipped version as my back up anyway. The various storage media are so cheap these days that I would only use this type of thing for sending over the www to keep the files size down, not for archiving purposes.