Users are reporting problems with Firefox accessing the Places database file, which stores bookmarks and history.

First thing to try is simply exiting out of Firefox and starting it up again. Check for an extra toolbar with the error message in the title of the following article: Fix "The bookmarks and history system will not be functional" error message. If you see that bar, Firefox either can't get access to the file -- possibly another process has locked it -- or the file has become corrupted. Before giving up on the file and nuking it (as described in that article), you could try a few other things:

(1) Try to release the file if it's locked

I found a post describing how to use Windows' Resource Monitor to try to figure out what program has opened a "handle" on the file (filter by places): https://superuser.com/a/643312

If it won't release, try a normal shutdown and/or restart of your system. If CCleaner normally runs at startup, see whether you can cancel that or create an exception for Firefox files.

(2) Run the "Verify Integrity" diagnosis and repair function

That's here:

Open Firefox's Troubleshooting Information page using any of these methods:

• "3-bar" menu button > Help > More Troubleshooting Information
• (menu bar) Help > More Troubleshooting Information
• type or paste about:support in the address bar and press Enter

Near the bottom, there is a section titled Places Database -- that's the file which stores history and bookmarks. Click the button labeled Verify Integrity. There may be a 10-15 second delay before results appear.

If all is well, the report that appears below the button should start with:

> Task: checkIntegrity
+ The places.sqlite database is sane
+ The favicons.sqlite database is sane
> Task: invalidateCaches
+ The caches have been invalidated
> Task: checkCoherence
+ The database is coherent

Does yours say the databases are sane and coherent, or something else? You can select and copy the report, and then paste it into a reply for review and comment.

Appreciate your help. Here is what it showed:

Task: checkIntegrity + The places.sqlite database is sane + The favicons.sqlite database is sane > Task: checkCoherence + The database is coherent > Task: expire + Database cleaned up > Task: vacuum + Initial database size is 10240KiB + The database has been vacuumed + Final database size is 10240KiB > Task: stats + Places.sqlite size is 10240KiB + Favicons.sqlite size is 2368KiB + pragma_user_version is 82 + pragma_page_size is 32768 + pragma_cache_size is -2048 + pragma_journal_mode is wal + pragma_synchronous is 1 + History can store a maximum of 94524 unique pages + Table moz_origins has 347 records + Table moz_places has 8680 records + Table moz_places_extra has 0 records + Table moz_historyvisits has 21173 records + Table moz_historyvisits_extra has 0 records + Table moz_inputhistory has 1 records + Table moz_bookmarks has 167 records + Table moz_bookmarks_deleted has 0 records + Table moz_keywords has 0 records + Table sqlite_sequence has 1 records + Table moz_anno_attributes has 2 records + Table moz_annos has 4 records + Table moz_items_annos has 0 records + Table moz_meta has 5 records + Table moz_places_metadata has 347 records + Table moz_places_metadata_search_queries has 0 records + Table moz_previews_tombstones has 0 records + Table moz_newtab_story_click has 0 records + Table moz_newtab_story_impression has 0 records + Table moz_newtab_shortcuts_interaction has 0 records + Table sqlite_stat1 has 23 records + Pages sequentiality: 53.4 + sqlite_schema: 32KiB (0.5%), 30.2% eff. + moz_origins: 32KiB (0.5%), 41.5% eff. + sqlite_autoindex_moz_origins_1: 32KiB (0.5%), 35.6% eff. + moz_places_extra: 32KiB (0.5%), 0% eff. + moz_historyvisits_extra: 32KiB (0.5%), 0% eff. + moz_inputhistory: 32KiB (0.5%), 0.1% eff. + sqlite_autoindex_moz_inputhistory_1: 32KiB (0.5%), 0.1% eff. + moz_bookmarks: 32KiB (0.5%), 54% eff. + moz_bookmarks_deleted: 32KiB (0.5%), 0% eff. + sqlite_autoindex_moz_bookmarks_deleted_1: 32KiB (0.5%), 0% eff. + moz_keywords: 32KiB (0.5%), 0% eff. + sqlite_autoindex_moz_keywords_1: 32KiB (0.5%), 0% eff. + sqlite_sequence: 32KiB (0.5%), 0.1% eff. + moz_anno_attributes: 32KiB (0.5%), 0.2% eff. + sqlite_autoindex_moz_anno_attributes_1: 32KiB (0.5%), 0.2% eff. + moz_annos: 32KiB (0.5%), 1.4% eff. + moz_items_annos: 32KiB (0.5%), 0% eff. + moz_meta: 32KiB (0.5%), 0.6% eff. + moz_places_metadata: 32KiB (0.5%), 37.1% eff. + moz_places_metadata_search_queries: 32KiB (0.5%), 0% eff. + sqlite_autoindex_moz_places_metadata_search_queries_1: 32KiB (0.5%), 0% eff. + moz_previews_tombstones: 32KiB (0.5%), 0% eff. + moz_newtab_story_click: 32KiB (0.5%), 0% eff. + moz_newtab_story_impression: 32KiB (0.5%), 0% eff. + moz_newtab_shortcuts_interaction: 32KiB (0.5%), 0% eff. + sqlite_stat1: 32KiB (0.5%), 3.9% eff. + moz_bookmarks_itemindex: 32KiB (0.5%), 4.8% eff. + moz_bookmarks_parentindex: 32KiB (0.5%), 5.3% eff. + moz_bookmarks_itemlastmodifiedindex: 32KiB (0.5%), 8.9% eff. + moz_bookmarks_dateaddedindex: 32KiB (0.5%), 7.8% eff. + moz_bookmarks_guid_uniqueindex: 32KiB (0.5%), 9.8% eff. + moz_keywords_placepostdata_uniqueindex: 32KiB (0.5%), 0% eff. + moz_annos_placeattributeindex: 32KiB (0.5%), 0.1% eff. + moz_items_annos_itemattributeindex: 32KiB (0.5%), 0% eff. + moz_places_metadata_placecreated_uniqueindex: 32KiB (0.5%), 17.5% eff. + moz_places_metadata_referrerindex: 32KiB (0.5%), 9% eff. + moz_newtab_story_click_newtab_click_timestampindex: 32KiB (0.5%), 0% eff. + moz_newtab_story_impression_newtab_impression_timestampindex: 32KiB (0.5%), 0% eff. + moz_newtab_shortcuts_interaction_timestampindex: 32KiB (0.5%), 0% eff. + moz_newtab_shortcuts_interaction_placeidindex: 32KiB (0.5%), 0% eff. + moz_places_visitcount: 128KiB (1.9%), 54.1% eff. + moz_places_frecencyindex: 128KiB (1.9%), 60.2% eff. + moz_places_originidindex: 128KiB (1.9%), 58.7% eff. + moz_places_altfrecencyindex: 128KiB (1.9%), 52.9% eff. + moz_places_url_hashindex: 160KiB (2.4%), 74.1% eff. + moz_places_lastvisitdateindex: 192KiB (2.9%), 70.6% eff. + moz_places_guid_uniqueindex: 224KiB (3.4%), 75.7% eff. + moz_historyvisits_fromindex: 224KiB (3.4%), 74.3% eff. + moz_places_hostindex: 256KiB (3.9%), 79.8% eff. + moz_historyvisits_dateindex: 384KiB (5.8%), 86.2% eff. + moz_historyvisits_placedateindex: 448KiB (6.8%), 87.6% eff. + moz_historyvisits: 544KiB (8.2%), 93.9% eff. + moz_places: 2400KiB (36.2%), 97.8% eff. > Task: _refreshUI