Clicking “Login Items” hangs Account pane of Sys Prefs for AD users in 10.5.2

Hi, I am attempting to change the "Login Items" on some Macs that are bound to our local AD domain. If I log in as a local admin account then I can change my own login items no problems. If I log on using an AD account, either as an AD admin with admin rights to the Mac, or by creating a mobile account and changing the rights to admin, or by just logging in as a standard AD user I cannot get past a hang when I click on "Login Items". Strangely I can quit System Preferences but not close the window or switch to "Show All". I get this behaviour regardless of the net connection - plugged in or not plugged in. Clues anyone? Tony Williams