1. Open Inspector
2. Highlight a node (click one)
3. Drag browser window from titlebar.
Highlighter panel moves with window. What actually happens, the highlighter panel stays pinned to its original screen location.
I did a browser restart after seeing this the first time and the problem went away. Before the restart, I was seeing similar offsets on some of my open pages while hovering over links. This may not be specifically related to the inspector.
Seems to be working okay for me in the latest nightly.
fixed by landing of bug 642471
Verified Fixed using
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:10.0a1) Gecko/20111020 Firefox/10.0a1 and
Mozilla/5.0 (Windows NT 6.1; rv:10.0a1) Gecko/20111020 Firefox/10.0a1.