[Neos] [neos 1.2] Setup error

[a s]

I'm trying to install neos 1.2.1 using symlinks instead of a virtual host, which was claimed possible by others for that web hosting service. Nevertheless I stumbled upon some errors I don't know how to interpret.

Setup is accessible and tells me "Your environment is suited for installing TYPO3 Flow". After a few seconds an error 500 occurs:
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Execution of subprocess failed with exit code 255 without any further output.
TYPO3\Flow\Core\Booting\Exception\SubProcessException thrown in file
Packages/Framework/TYPO3.Flow/Classes/TYPO3/Flow/Core/Booting/Scripts.php in line 526.
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And:
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Fatal error: Declaration of TYPO3\Neos\Command\NodeCommandControllerPlugin::invokeSubCommand() must be compatible with TYPO3\TYPO3CR\Command\NodeCommandControllerPluginInterface::invokeSubCommand($controllerCommandName, TYPO3\Flow\Cli\ConsoleOutput $output, TYPO3\TYPO3CR\Domain\Model\NodeType $nodeType = NULL, $workspaceName = 'live', $dryRun = false, $cleanup = true) in /.../Packages/Application/TYPO3.Neos/Classes/TYPO3/Neos/Command/NodeCommandControllerPlugin.php on line 31
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I think I checked the requirements so far, and tried a lot of nonsense without any luck. One thing I can't use is sudo to set file permissions.
Now before this gets worse ...