Shoutbox

They either are 100% corrupted...
It is not because certain recovery software says files are recovered that they actually are recovered. The filenames may be recovered, but the actual contents may not (many recovery packages, even professional ones, can not automatically detect this) because it was already overwritten by other stuff.

Or they are encrypted Messenger Plus! log files.
But there is absolutely no way you can decrypt them if you do not know the correct decryption password. There is also no way to recover/crack the password; it is not stored anywhere.

But if the contents you've showed in your post is the beginning of such a recovered file, then I can already say for sure that those are not encrypted Messenger Plus! log files either (an encrypted log file always starts with the string 'MPLE'). So the only conclussion left is: completely corrupted.