I noticed that the last item on any level of the site tree (or should I say the last child of any item) doesn't highlight correctly when you select it.
This is because the .last class is overriding the background for the .current class.
On line 50 of /jsparty/tree/tree.css, change
ul.tree span.a.last {
to
ul.tree .a.last {
It makes the rule is less specific, so it's overwritten by .current and the background colour appears as it should.