There seems to be some issues while trying to run Altiris DAgent on a Vista box that has Service Pack 1 installed. You can read a forum post on the Altiris forums here. Supposedly if you’re running DS SP1 the DAgent on Vista Service Pack 1 works fine but if you’re running DS SP2 it causes DAgent to crash. Quote from the end of the thread by Anthony Russo says

” Altiris now part of Symantec is working on this problem. The incident number 194760.”