What exactly did you do to upgrade textures? I'm assuming you're talking about terrain / model textures. If so, it wouldn't be a UI problem, necessarily, and most likely not, unless a secondary effect of a UI. With the same assumption, the problem is most likely a texture file, or a memory issue (i.e. bad memory location(s), not enough memory for the textures, etc.).
If it's something else you're upgrading, and even if not, what UI are using? If it is the default one, delete all the files in the everquest/uifiles/default directory and do a thorough file scan to make sure they are updated. You might also look at everquest/UIErrors.txt file.
Just now looking at my UIErrors.txt file, it looks like they've made more changes to the UI since the last announced change, as I have more errors than normal on my custom UI. All of them only relating to the new Item Display window however.
More details almost always help.
Yther Ore.