Weird tab bug in Firefox 2.0

In Firefox 2.0, with two or more tabs open, roll the mouse pointer over a tab caption and up into the Bookmarks Toolbar. Sometimes the icons and text from the Bookmarks Toolbar will overlay the tab caption (see image below). Doesn't always happen, but has happened several times. Looks like a bug?

Update: Another example, this one after Alt+Tab switching from another app back to Firefox.

Tags: Firefox 2.0