I click the icon on my desktop, it fails to connect to the update server. Game won't start.

Discuss.

What kind of internet connection/provider do you have?

Are you at a college/university? Router? what kind of firewalls?

done a packet trace to the server?

The update servers are operational. It's almost certainly a firewall or proxy configuration issue at/near your end, as zik says (college dorm? apartment or condo network? etc).

The game updater connects outbound to remote TCP port 21024. Once the game is updated, the client then connects to remote UDP port 21141. If you have a local network admin, they may be able to configure the firewall to permit this.

If you are on a Mac... you need to drag vendetta.app into your applications folder and start it from there.
We had a bunch of ppl before trying to start Vendetta from mounted dmg image on dektop.

I'm just an average Joe with a home router and a couple of computers using a cable modem. It worked one day, and then didn't a few days later.

I assumed someone was working on the game and it was down. Other games work fine for me. I'll double check my end again, thanks.