Fixing resolution
 

So, when you first launch the client and you click options (before you log in), then your options are limited for which resolution you want.

Once in game, you can pick all the major resolutions. My resolution is 1920x1080. I pick this option in-game and it switches fine for about 1 minute then randomly it switches back.

How do I stop this?

Open up eqclient.ini in the root directory of your EverQuest folder (make sure you have admin privs to the file). You should see a section similar to this:

[VideoMode]
WindowedWidth=1280
WindowedHeight=800
Width=1280
Height=800
FullscreenBitsPerPixel=32
FullscreenRefreshRate=0

Change Width=(value) to Width=1920 and Height=(value) to Height=1080. Save the file and reload. Your resolution should be set.

You can also use my installer (see my signature) and pick option (6) then select which resolution you want to play at (this will reset your keybindings).