I have uploaded a new version of the WoW UI Designer program. The changes are listed below. You can either get it from this site or use the Update Program feature if you are using version 1.0.300.3.
1.0.300.4: Beta Release 10
* Fixed a bug with the texture browser not showing.
* Redid some of the multi-document find functionality.
* Updated structure view so that it provides some help whilst editing XML files.
+ Added file modified detection to allow easy reloading/deleting of files modified outside the editor.
* Updated context menu of editor to add more functions.
* Options dialog now working, editor customization available again!