Thanks for getting back.
"empty" is nothing: My library in the left pane and pale blue on the right pane with no text or graphics at all.
My software, FF3.5 on Vista.
chrome://epubreader/content/library.xul (as per you request) produces just pale blue blank screen.
chrome://epubreader/content/catalog.xul is a 2-pane display.
The error console: 3 messages following your instruction (below).
Error: uncaught exception: [Exception... "An invalid or illegal string was specified" code: "12" nsresult: "0x8053000c (NS_ERROR_DOM_SYNTAX_ERR)" location: "chrome://epubreader/content/library.js Line: 18"]
Error: not well-formed
Line: 19, Column: 35
<html:td>Christopher Golliday & Melissa Golliday</html:td>
[ a pretty green line pointing up at the 'M' of Melissa] Ah ha!
nLocationChange]" nsresult: "0x80570030 (NS_ERROR_XPC_JSOBJECT_HAS_NO_FUNCTION_NAMED)" location: "<unknown>" data: no]