[TYPO3-english] pt_extbase bug getting a FATEL ERROR (ExtensionManagementUtility)

[Sebastian Gärtner]

Fatal error: Cannot use TYPO3\CMS\Core\Utility\ExtensionManagementUtility as ExtensionManagementUtility because the name is already in use in /typo3temp/Cache/Code/cache_core/ext_localconf_b65ebe542dd9cbb86444044a588bedab4f056e2d.php on line 1449

Am trying now to install old versions of the extension. Meanwhile site is down and i have no idea whats happening.