Latest weeks I got many bug reports about error like this:
Database Error: DB Error: constraint violation(update `mp_settings` set
site_name`='XXXX',`site_description`='YYYY',`currency_symbol`='$',`user_accounts`='1',`approval_required`='0',
`admin_email`='manager@example.com',`html_email`='0',`use_fckeditor`='1', `secret`='jdb314tab518',
`interlaced_images`='0',`palette_images`='0',`site_down`=NULL, `blog_comments`='0',
`expires_check_at`=NULL,`multiple_grid_pages`='1',`grid_columns`='1',`rss_latest_pixels`='10',`rss_top_pixels`='10',
`rss_blog_articles`='0',`pixel_list_by_clicks`='0',`seo_status`='optimized',`link_to_us_enabled`=NULL,`upload_images`='1',
`order_image_galleries`='ksort#SORT_REGULAR',`pixel_list_enable_images`='1' where `id`='1'
[nativecode=1048 ** Column 'site_down' cannot be null])