When I run Vendetta, the updater window comes up, the progress bar quickly progresses across the screen a couple times, and I'm shown the changelog and a message at the very bottom of the window: "Update Failed".

And then when I click "Play Vendetta", it crashes, with the message "Segmentation Fault."

What could be causing that?

I guess it's probably not a network cause it can download the changelog.

Do you have enough disk space? Maybe something got corrupted in a way that the updater can't handle.. try removing ~/.vendetta and reinstalling.

I think it may have been because I installed it for root, rather than my user. I reinstalled, and it works now.