The same thing happened to me too. I am using self hosted WP 3.4.3 and yesterday when I was trying to modify my widgets. Every time I added a widget another widget disappeared. Now only text widgets work and all other widgets disappeared. They are not deactivated, they just will not display in Chrome, Explorer, or Firefox.
Put define('WP_DEBUG',true); in wp-config.php and see if you get any messages that might help.
I got error messages that gave me some ideas.
It says
Notice: register_sidebar_widget is deprecated. Use wp_register_sidebar_widget() instead in /home/limere5/public_html/wp-includes/functions.php on line 2638
but I did not find the deprecated code
The deprecated code is not where the message says it is. It is in the theme (probably functions.php) or in one of your plugins. That shouldn’t cause your widgets to vanish though.
Make sure that your theme and widgets are up to date. You may have a version conflict.
Try disabling and re-enabling your plugins.
Switch themes and see if the widgets work with Twenty-Eleven.
Do you have an URL?
