If your copy of Dawn of War 2 has been crashing in Windows Vista - well you aren't alone. Over at the official community blog the folks of Relic acknowledge an issue with 32-bit Vista and an out of memory bug. The team is working hard to fix it, but in the meantime it's suggested you reduce your texture detail and effects fidelity to medium to help reduce the risk of a crash.
Speaking of patches, the devs pushed out a small patch that fixes campaign corruption. This patch should automatically download via Games for Windows Live or Steam.