This should be a fairly simple question.

When I type "emacs test &" from my regular username, a new emacs windows opens up and everything works fine.

When I type the same thing fromt the root account, I get:

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified
emacs: Cannot connect to X server :0.0.
Check the DISPLAY environment variable or use `-d'.
Also use the `xhost' program to verify that it is set to permit
connections from your machine.

I tried to run xhost, but I get the same error.

The display env variable for each account is :0.0

Anyone know what's up?

How are you using the xhost command? Just running "xhost" will not change anything, it only displays which hosts are allowed to connect.

If you are logged in as a standard user, then using su to get root access, then trying to open an X window on your desktop then you will get this.

The way to get around it is to run "xhost +<hostname>"
not literally of course, you need to sub in your hostname for <hostname> or use "localhost" if you are doing this on the same machine.

Some might tell you to just use "xhost +", which is bad form, you should always specify the name of the host you wish to allow access to.