If Typo3 ever tells you: "You are not allowed to create directories" never trust your boss, do not search permission problems in the underlaying OS. Go and activate the filesystem checkboxes for the specific user in the user manager.
This is especially true if you are using a LDAP backend.
Today i had to copy a Typo3 installation, after dumping and restoring the database, copying the files and changing the localconf.php, the frontend was working nice.
Just the backend did not work, it only returned a blank page. No content.
Debugging with lynx returned a Redirect to http:// ...
The solution? lockSSL was set to 1, which, in connection which an explicit IP configuration of the webserver, resulted in wrong wrong (the empty http://) redirects.