Infragistics

Widget-fixer works by recalculating the string lengths of the widget strings and updating 
the relevant numbers in the database so that your widgets will load again.
Disclaimer 
This plugin is provided “as is.” It is free software licensed under the terms of the [GNU General Public License 2.0 (GPL)] (http://www.gnu.org/licenses/gpl.html “GNU General Public License 2.0”). It is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Infragistics is not liable for any damages or losses.

Widget Fixer

Widget-fixer fixes your widgets after you change to a new siteurl.

Kerfred

This plugin fixes the serialized strings in the wp_options table. It recalculate the length of each strings. 
It can be useful after a migration if you have done a global search/replace in the SQL dump.
Major features include:
<ul>
<li>Repair the options table</li>
<li>Repair the postmeta table</li>
<li>Restore the lost text widgets</li>
</ul>
<h3>Translations</h3>
<ul>
<li>English (default)</li>
<li>French (fr_FR)</li>
<li>other can be translated</li>
</ul>

FG Fix Serialized Strings

Fix the broken serialized strings in the options and postmeta tables

Widget Fixer vs FG Fix Serialized Strings