Hi, this is my first post to the forum.
I 've had the same problem after upgrading to SP1, but it didn't just affect Vista and Win2008. I had XP computers breaking their AD computer account also. I *think* the Altiris client agent was duplicating computers on the domain. You'll need to reset the accounts in AD, and re-enable them if they are disabled.
I have fixed this problem by applying the MP1 patch to DS 6.9 SP1. This will upgrade all the agents to build 366. However, I had to install a Webconsole that I don't need, to allow the MP1 patch to install, then remove the webconsole afterwards. Initially I thought I did not need the MP1 patch because, if you don't have a webconsole, MP1 will not install. This is a bad design feature.
I also had to create new images using machines which had the 366 agent on them. These images are deploying successfully. I already tried editing my existing images to replace the agents, but that has not been reliable enough.
~Mike~