Do this step and you see bug:
1. Open mail box (he open in left panel)
2. Open inventory Window (right panel)
3. Open ANY massage from inbox (inv go left, message will open in right panel)
4. Press REPLY button in mail window (new mail in right, old in left)
5. Close old mail (new will go to left)
6. Open inv and try right click to attach any items. Item will use instead attach :-)
I see that bug from NY. Dont know for early time.