You need to make sure to add the file to the eq2ui_mainhud.xml
Code:
<include>eq2ui_mainhud_spells.xml</include>
Also, make sure you edit eq2ui_mainhud.xml with Notepad (or a file editor that shows special characters. The first 2 lines of eq2ui_mainhud.xml are seperated by a small box:
Code:
<?xml version="1.0" encoding="utf-8"?>
<Page ismodule="true" Name="MainHUD" PackSize="1,1" PackSizeProp="0002/0003,0002/0003" ScrollExtent="1024,768" Size="1024,768" Visible="false">
You cannot see it here, but if you open the file in Notepad, you'll see what I mean. If that little box isn't there, your UI won't work correctly (just a forewarning).
**Edit** I've attached a screenshot of what I mean...