hello, had already searching the documentation, forum, on google and was when I found the following, and although I'm not sure that's the same error so it seems:

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http://www.open-realty.org/bugs/

Doing a ptext search that fails or refining a search results in htmlspecialchars() error

Empty price field causes warning errrors in PHP 5.3
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Anyway, I had to search back in the forum and I have never read the messages but the only conclusion I have reached is that replacing a file by that of search.inc.php core version is 2.5.7 may resolve, but I paracer a correct solution.

Thanks and sorry for the inconvenience