Xlib: Invalid MIT-MAGIC-COOKIE-1 key

When I executed xhost + command on a Solaris box as root. I got the following error:

root@apps11i # DISPLAY=apps11i:1
root@apps11i # export DISPLAY
root@apps11i # xhost +
Xlib: connection to "apps11i:1.0" refused by server
Xlib: Invalid MIT-MAGIC-COOKIE-1 key
xhost: unable to open display "apps11i:1"

This error is the correct behavior because xhost + command can be executed by that user who has started the X session. Solaris is protecting a particular user's processes by disallowing other users to control it. In my case it was a vnc session started through a different user. Once I logged in as that user

root@apps11i # su - applmgr
applmgr@apps11i # xhost +
access control disabled, clients can connect from any host