For the mac users, this problem is new. To fix it, you will need to reinstall Vendetta Online.

Or you can download this file:
http://download.vendetta-online.com/Vendetta
and place it in your Vendetta.app/Contents/MacOS folder (to overwrite the Vendetta file that is already there).
And then you will have to change the file mode to executable:
At a terminal, type:
chmod 777 /Applications/Vendetta.app/Contents/MacOS/Vendetta

Or change Applications to whereever you installed VO to.
For example, if you installed it to your desktop:
chmod 777 ~/Desktop/Vendetta.app/Contents/MacOS/Vendetta

Thanks for the fix!