Strange Highlighting Behavior in the Article Pane

(edited to use correct names of the panes)

When I select a feed from the feed pane, and then click on an article in the title pane, it's highlighted as light grey. If I then click back on the feed name in the feed pane, and then back on the article in the title pane, it highlights the correct Windows setting of dark blue. I'm unsure if this is NewsFox or Firefox or XUL related, but has anyone else had this problem?

Windows XP Pro SP3
Firefox 3.1 Beta 3 (which may be a problem)
Newsfox 1.0.5rc1