[Joyelle]

Definitely don't replace your default directory. That's the fallback if your UI load fails and if the default has an error it will make your game crash as soon as you login.

Which specific new windows are you trying to use in this custom folder? If you are getting the pieces from the EQInterface website they are likely written for features that do not exist in the titanium client or are disabled on P99. Some of them may also be dependent on files with different code but the same file name (EQUI_animations.xml is a common culprit in clashes between custom UI pieces).

Spells06.tga and Spells07.tga are 2 of the files for buff/spellbook icons. If you're trying to use a custom spellbook, buff window, song window, casting window, target window or pet window, any of those could be calling on these 2 files. To resolve those error lines, try copying and pasting those 2 files from your default folder into the new custom UI folder.

The 3rd line is where your fatal error is occuring though, not sure if c/p of those 2 files will resolve the 3rd but it should at least narrow it down.

Disclaimer: not a UI/xml expert but i've tinkered with custom UIs since they were introduced on live. Any success i've had with them comes from hours upon hours of frustrating trial and error... and crashes.