What OS you are running shouldnt really matter. Only reasons why it should crash is
1) improper mod installation. Try re-installing the mod, and do not run other mods on top of SoA2
2) Running mod with "wrong" version of Diplomacy.
3) You are hitting the 2 gig ram limit. Try lowering your video settings. If your rig has 2 gigs of ram, or less then you should definitely lower the settings. Vanilla Diplomacy 1.21 uses about 1.4 gigs of ram (give or take depending on map size, how many ai's etc) at maximum settings. The Dip 1.2 patch was supposed to fix the 2 gig dump issue. The mod is rendering 5 different factions. Not 3 like Vanilla. So we are kinda pushing the limits a bit.
I havent had any time to look at the latest mod update yet. But from brief glance there are quite a few duplicate files just in the textures folder. I am also wondering if any of the diplomacy 1.2 graphic fix's are being overridden. "IF" i can get some spare time ill check this out.
As far as diplomatic victorys crashing the mod. there may be an entity that the mod isnt digesting well. One of the code monkeys will have to look at that.
Seriously?? You are playing the Tutorial with the mod enabled?