So all your projects have an error when you export? 
You didn't answer my original question:
"If you create a new project and export a simple track to mp3 does it work for you?"

Absolutely yes,i tried it yesterday.
Empty 4tracks project with a audio file.
No plugs o vsti,when i export in mp3 or wave i have an internal error during mixdown
Again same test in Splat is perfect
Again before CbB update all was perfect

meng
I don't use Sonar, I use CbB :-)

 
 
Ha, ha.. You know what I meant :)  old habits are hard to break, and I still think of the "DAW"  as Sonar. 
And glad to know your using it too. Be careful, it's addictive...
 

GIM Productions
Absolutely yes,i tried it yesterday.
Empty 4tracks project with a audio file.
No plugs o vsti,when i export in mp3 or wave i have an internal error during mixdown
Again same test in Splat is perfect
Again before CbB update all was perfect

This is possibly something install or system related then. Maybe even language or file name related.
There are no changes whatsoever to export in this version.
 

Ohhhh the language.....is the only things added in update,the language before update was english now is italian...
I hope that bandlab staff can investigate...
Thanks Noel

GIM Productions
Ohhhh the language.....is the only things added in update,the language before update was english now is italian...

I've got the same problem.
I'm British but live in Italy, so my OS is Italian. I'd prefer my version of Sonar to be in English, but after the update it went to Italian - any ideas on how to change it back?

The language may be set using the Cakewalk Command Center (this works for CbB too because SONAR and CbB use the same registry entry) or by setting HKEY_LOCAL_MACHINE\SOFTWARE\Cakewalk Music Software\Language to English using regedit. CbB overriding the existing setting is a known problem and is being addressed.
 
If the language is changed please report back whether is makes a difference or not.
 
When reporting problems is it useful to state the software version, "latest update" is not as useful. The current version of CbB is 24.04.1.28. The information is found on the About screen.

GIM Productions
Ohhhh the language.....is the only things added in update,the language before update was english now is italian...
I hope that bandlab staff can investigate...
Thanks Noel

I am BandLab staff :) So if you change the language to English does your export problem go away? Please report back. See scook's post above to change the language.

Noel Borthwick [Cakewalk]

GIM Productions
Ohhhh the language.....is the only things added in update,the language before update was english now is italian...
I hope that bandlab staff can investigate...
Thanks Noel

I am BandLab staff :) So if you change the language to English does your export problem go away? Please report back. See scook's post above to change the language.

Sorry Noel,for me you are the boss not the staff ....
I tried every other setting,but after the update at 24.04.01 build 28 the export not work.......
I have done the tests in some full prj and in empty prj (no plugs)with and without 64 bit export option (Bitflipper advice)....
I have changed the language from italian to english with CCC but not work....
For my knowledge.......i can't see the language folder in regedit...is it normal?
In Sonar Platinum (the best DAW in the world )is all perfect!
I would like to thank the CbB support who sent me a mail for the problem,nice and kind guys!
Many thanks and i will inform you about the developments.

Please include the exact steps you are performing to export including the actual folder name you are trying to save to.
Does bounce to track work for you? If that works exporting to a wave file at 32 bits should definitely also work since its essentially the same code.
 
Based on the error message and the fact that it happens in all languages, my hunch is that this is a permissions issue with the folder location you are saving to.
Try running CbB as an administrator and do the same operation and report back as well.