Try it with the 'custom' skin and see what you get. If the custom skin produces an error I think you'll need to talk to your host about it, but maybe not. It's possible somewhere you have a corrupted file. Corrupted in your zip, or while unzipping, or while uploading to your server. Anyway first guess is that you should see what happens with the custom skin.

Yeah you got something funky happening in your skin. "Please, do not access this page directly." pretty much screams "I'm a broken skin!!!" so try the custom skin and see how it goes.