Which release of AjaxSearch do you use ?
If you use 1.8.2 or 1.8.3:
==== php_mbstring extension
&mbstring [0 | 1]
1 - mbstring extension available (default)
0 - don't use php_mbstring extension
The php_mbstring is supposed to be loaded.
If html charset page is "UTF-8", php_mbstring extension should be loaded for language which
need a multi-byte representation.
If the extension is not available for the PHP server, some charset like ISO-8859-1 (latin1) could be used.
With UTF-8, a message "Php_mbstring extension is required" when &mbstring=`1` and the extension not loaded.
In this case load the extension or set the mbstring parameter to 0 if you couldn't load the extensionSo use &mbstring=`0`
