Is there a mod out there for the achievement window? I've looked around and am not able to find anything. Right now, when I open it, I get a black window with a tree. I was told that there were other tree's to use my points on but I can't "see" anything.
Are you using a lot of different pieces or a full UI set?
Some custom UI pieces require you to <include> them in a custom eq2ui_mainhud.xml file. If you aren't using any of those kind of pieces you don't even need a custom eq2ui_mainhud.xml.
Go to the default UI folder and open eq2ui_mainhud.xml in a text editor. You'll see a big list of <include> statements. This tells the UI engine all the children of the mainhud object.
Then open your eq2ui_mainhud.xml file and compare the list of <include> statements. The order doesn't matter but you're probably missing the recent additions like: