4
Ok, if you go to blocks and activate the "Themes" block, and then go to groups and make sure anon users can access this block.
Then go to general preferences and make the problem theme, and your default theme selectable, that will allow us to have a look.
Did you make any alterations to the theme? Also check that the file structure you uploaded is correct, you can compare it with the others.
Try clearing out your templates_c folder, this is the cache (leave index.html intact in this folder)
Also, if you switch on php debug in general preferences and paste the results here this would help, perhaps you can do that later if we can't detect any obvious reasons for the problem.
regards