they are working on it to make it Vista compatible..they have it working for most people, but there are still a few bugs...try their technical service division..they are much more qualified to handle this than anyone here on this forum.
If you don't know how to reach them, I can give you a link.
if you are still having issues, you can try compatibilty mode for xp. just right click on the DAoC shortcut, click properties, and run in compatibility mode for XP. a buddy of mine did this when vista came out and had almost no issues.