So I had this issue with the retail version of the game, and assumed it was a DRM issue, with the game trying to connect to the Ubisoft servers that don't exist anymore, but now I'm having it with the GOG version as well.

So I bought the game DRM free on GOG, and played for a few hours, got through the first assassination, no issues (farther than I ever got with the retail version). I booted it up today, played for a couple hours, and then the game crashes. Just stops, midgame, and gives me an "Assassin's Creed game has stopped working" message. Ever since then, the game has been crashing pretty regularly every 15 or 20 minutes or so. It's getting real frustrating.

Anyone else had this issue? Know of a solution? Any help would be appreciated. Thanks!

Nevermind, I seem to have fixed the issue. Set the compatibility mode to Vista and blocked the game on my firewall, and haven't had a crash since.