take an example there
on click of Baccara the selection box around it shows. However if u put instead of Baccara empty value, the selection box around it doesnt show on selection click. This problem only in ie 7.Not firefox or chrome.
That's looks the problem with IE 7 handling of 100% for empty td.. Try to set min-width using .rich-tree-node-text css class. If not helps try to add div around the text with min-width in px specified.
I haved worked around it by setting background-color, and the border making it 0 in all cases