I just had the same problem after uploading a working website to my hosting provider. This also turned out to be a problem with upper-/lowercase of the config files.

I found out that  I could even upload admin.config TWICE to my hosting provider if one filename starts with uppercase and the other one with lowercase. I don't know if this has got to do with unix/linux or something else, but it's a bit misleading.

 

I prefer to keep everything lowercase anyway, and that solved the problem. Still got another one now (menus cannot be loaded???) but I suppose that hasn't got anything to do with this...