TYPO3 Core

Over months this T3 was working flawless. From yesterday to today nothing was changed on server nor in settings.
Opening a tx_news with an attached file with an umlaut in filename results in:

WARNING! FAL resource problem detected. The field "media" has been reset to an empty value in order to prevent fatal, unrecoverable errors. The actual message is a TYPO3\CMS\Core\Resource\Exception\FolderDoesNotExistException which states: (1320575630) Folder uploads/tx_news/2014-07-07_Verbrauchsg%C3%BCter.jpg does not exist.

• While the file is correct uploaded to uploads/tx_news/2014-07-07_Verbrauchsgüter.jpg in filesystem and the relation in tx_news_domain_model_media is correct utf8
• The file is directly accessible with http://my.domain/uploads/tx_news/2014-07-07_Verbrauchsg%C3%BCter.jpg

1. LocalConfiguration.php has

'SYS' => array(
.
.
'UTF8filesystem' => '1',
'systemLocale' => 'de_DE.utf-8',
't3lib_cs_convMethod' => 'mbstring',
't3lib_cs_utils' => 'mbstring',
.
.
)

1. Fileadmin

Works without problems on files with umlauts. Thumbs are generated and files are accessible.

1. T3 Version

6.1.9 && 6.1.10 tested

1. PHP Version

5.5.14 && 5.4.30 tested

No idea where this shall come from. Any help welcome.