Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes). See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If it does work in Safe-mode then disable all your extensions and then try to find which is causing it by enabling one at a time until the problem reappears. You can use "Disable all add-ons" on the Safe mode start window. You have to close and restart Firefox after each change via "File > Exit" (on Mac: "Firefox > Quit") --- Looks like a problem with checking bookmarks for Microsummaries to see if there are updates.

How many bookmarks do you have? Do you have other problems with bookmarks?

Copy and Paste this code in the Code field in the "Tools > Error Console" and click the "Evaluate" button to cleanup and compress the places.sqlite database file. Components.utils.import("resource://gre/modules/PlacesDBUtils.jsm");PlacesDBUtils.checkAndFixDatabase();

To answer your questions:

1. How many bookmarks do you have? -- Without counting, at least 2,000 bookmarks. And many folders and sub folders.

2. Do you have other problems with bookmarks? --

Date of the last HTML export: 03/22/2010. Size: 4, 443 KB. The number of bookmarks has grown since then. I attempted to "move" a few folders since the last HTML export and these folders appear to be corrupted - I cannot delete them. Since then the "HTML export" function has not worked. Is there a way to "compress" the bookmarks? I remember, years ago, compressing files eliminated corruption.

The only updates I am aware of are Firefox and "NoScript" (latest: 1.9.9.77)

3. Result of pasting the following code into Tools\Error Console:

Components.utils.import("resource://gre/modules/PlacesDBUtils.jsm");PlacesDBUtils.checkAndFixDatabase();

INTEGRITY ok - - - CLEANUP - - - VACUUM places.sqlite: 7925760 byte - - - STATS places.sqlite: 7925760 byte moz_bookmarks: 6377 moz_bookmarks_roots: 5 moz_keywords: 0 sqlite_sequence: 0 moz_favicons: 708 moz_annos: 5670 moz_anno_attributes: 8 moz_items_annos: 4468 moz_places: 10722 moz_historyvisits: 8871 moz_inputhistory: 8 - - -

 -----------------------------------------

After attempting "Export HTML"

Error: uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIPlacesImportExportService.exportHTMLToFile]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: chrome://browser/content/places/places.js :: PO_exportBookmarks :: line 395" data: no]