TYPO3 Core

When I want to save accentuate character in a Flexible Content, in the label name, etc. Typo3 return me an error : Catchable fatal error: Argument 2 passed to t3lib_div::array_merge_recursive_overrule() must be an array, string given, called in /home/grisim/public_html/t3lib/class.t3lib_tcemain.php

This problem was happening on 3 servers with this configuration:
- Php 5.2.25
- MySQL 5
- LibXML 2.6.32
- Typo3 4.0.3 / 4.1.5 / 4.2

I have no problem with this configuration:
- PHP 5.2.25
- MySQL 5
- LibXML 2.6.16
- Typo3 4.1.5

and I have no problem with this configuration:
- PHP 5.2.25
- MySQL 5
- LibXML 2.6.27
- Typo3 4.2

I think the problem was in the LibXML (maybe in a fix security of 2.6.30 version)

(issue imported from #M8350)