I installed silverstripe 2.3.3 at least three times on my localhost and never had any problems. Today I tried to install it again for a new project but the installation failed. At the point where the installer tries to create the database tables I get an error message. I attached the picture.
Once more I have to answer my own questions ;) Maybe this solution is helpful to someone else.
I have to pitty my new SnowLeopard for not letting me install SilverStripe on MAMP anymore. I still used the old MAMP 1.7.3 which was not compartible to SnowLeopard, though my old installations still worked.
As I updated MAMP to 1.8.3 and rebooted my computer everything worked well.