Upgrade 6.1-> 6.2 Kppp fails to start

["Paul R. Brandariz" <brandari lore kla-tencor com>]

After upgrading RH6.1 to RH6.2 kppp failed to start with

Xlib: connection to ":0.0" refused by server
Xlib: Client is not authorized to connect to Server
kppp: cannot connect to X server :0

Now I know I can do

    xhost +

and use kppp but why did it failed at all.
Wouldn't I own the display at login ?

What changed ?