I have just downloaded the game, and started up the application for the first time. As I was expecting, the updater came up and told me it was about to start updating.

<<Patching version vendetta-1.7.14 to vendetta-1.7.41...>>

Not even two seconds later it states

<<can't open Contents/MacOS/Vendetta! aborting!>>

What exactly do I need to do to correct this problem?

Be sure you have copied Vendetta off of the disk image and into your applications folder.

This could be where the main problem stems from. I went ahead and downloaded a trial of the game off of the website. It originally saved the thing to my desktop as a .dmg, which when open has the readme, and the Vendetta starter file inside. I am more than a bit suspicious that something is missing.

I managed to correct this problem.

Yes, all you need to do is drag the Vendetta application to your desktop (or wherever you want to install it to) and run that copy.