Launching apps hided

If i run this code in 10.5.x then it opens small on screen keyboard:

tell application “System Events” to open alias “Macintosh”

But if i add it to Login Items list in Accounts Pref Pane then it launches without showing keyboard.

How i can force it to launch without showing up in AppleScript?

Similar thing happens when i try to open apps which don’t appear in Dock. Those apps show their window and i can’t find a way to hide them using AppleScript.