Hard to tell. When ? where ? how ? do you see that message ? what versions of joomla, CB, PHP ? what did you do to get it ?

As general reply to such errors:

looks like your files got corrupted somewhere on their way, and the built-in files validation somewhere failed.

Please make sure to transfer in binary mode instead of automatic or text, in case you are using FTP somewhere.

Also please make sure your PC and webbrowser does not have viruses/trojans which would try to change files.

Then re-try, maybe using a different browser (maybe an extension of your browser does that)

Hard to tell, without knowing more of the first questions...

(Moving thread to support forum).