Open a PB.
Right-click on the PB's tab and select "Open in a floating window"
Right-click on the PB's tab in the floating window and select "Dock this tab"
Attempt to rebuild the book (while it is still open).
Build Fails, "Could not remove existing resource."

Closing all panels and starting again doesn't work. Have to restart Logos.
Here's the PB build log: 2744.PBB_15a2fce72c02499a9757fdfad1dad779.log
And here's the Logos log file: 4401.BuildFailed20120121.zip