TYPO3 Core

Unfortunetly I encountered this PHP-Error when logging into the backend with TYPO3 6.0b2:

Fatal error: Cannot use string offset as an array in /var/www/typo3_src-git/typo3/sysext/core/Classes/Resource/ResourceFactory.php on line 145

Call Stack:
    0.0002     643648   1. {main}() /var/www/typo3_src-git/typo3/index.php:0
    0.0003     671656   2. require('/var/www/typo3_src-git/typo3/init.php') /var/www/typo3_src-git/typo3/index.php:36
    0.2013   18314072   3. TYPO3\CMS\Core\Core\Bootstrap->initializeBackendUserMounts() /var/www/typo3_src-git/typo3/init.php:100
    0.2013   18314776   4. TYPO3\CMS\Core\Authentication\BackendUserAuthentication->returnFilemounts() /var/www/typo3_src-git/typo3/sysext/core/Classes/Core/Bootstrap.php:784
    0.2067   18572528   5. TYPO3\CMS\Core\Authentication\BackendUserAuthentication->getFileStorages() /var/www/typo3_src-git/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php:1853
    0.2067   18572528   6. TYPO3\CMS\Core\Authentication\BackendUserAuthentication->initializeFileStorages() /var/www/typo3_src-git/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php:1586
    0.2141   19154000   7. TYPO3\CMS\Core\Resource\StorageRepository->findAll() /var/www/typo3_src-git/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php:1514
    0.2167   19896656   8. TYPO3\CMS\Core\Resource\StorageRepository->createDomainObject() /var/www/typo3_src-git/typo3/sysext/core/Classes/Resource/StorageRepository.php:132
    0.2167   19896656   9. TYPO3\CMS\Core\Resource\ResourceFactory->getStorageObject() /var/www/typo3_src-git/typo3/sysext/core/Classes/Resource/StorageRepository.php:196
    0.2167   19896816  10. TYPO3\CMS\Core\Resource\ResourceFactory->createStorageObject() /var/www/typo3_src-git/typo3/sysext/core/Classes/Resource/ResourceFactory.php:128
    0.2167   19896984  11. TYPO3\CMS\Core\Resource\ResourceFactory->convertFlexFormDataToConfigurationArray() /var/www/typo3_src-git/typo3/sysext/core/Classes/Resource/ResourceFactory.php:212

I really don't know what's going on there. I did not touch any file. I am using Ubuntu 12.04 with latest PHP 5.3 available for it.

Perhaps someone knows the answer to this strange error.
Alex