Hmm, have not seen that before. But, since you said you're using UI builder, was the bank window the only thing you copied, or did you use the entire saved UI that UIBuilder generates? It looks like it mangled the icons in some way so that they're no longer functioning as bag slots (the 'dust cloud' background and the little golden box around inventory icons are all added / generated in-game using art in one of the DDS files)
Try making a folder and copy only the bank window that you modified into it, and then update your EQ2.ini to point that that folder. All the other files should be pulled from default, so if (as I'm guessing) it's UIBuilder messing up one of the other files things should look OK then. That program has a bad tendency to not save everything as it should, when it comes to things like styles, etc.
What I do when working with UIBuilder is to have a separate directory where I work and save things into. To actually test files in-game I copy them to a different directory, and only copy the files that I've changed, that way you avoid the UIBuilder wonkiness.
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