Ok, my provider did fix the fault and now everything is back again, also the testing site. :-)
The main mobiki site is actually up and running again. All my domains do run well if configured for Apache/PHP5.3, but do actually not run with the providers setup for PHP 5.4 as FastCGI server. So the testsite is still down for to be a testbed for the provider. I'm very sorry for that! :-( I will inform you as soon as the test site is up again.