MY_Controller not found - once again

Hello,

I know this question is asked and answered a couple of times before, but I still run into this Error when uploading my files to the production server.

On my laptop (xampp), everything works just fine, but on the Linux-Server I get a blank page and this dumb error:

ERROR - 2016-04-29 18:41:28 --> Severity: Error --> Class 'Main_controller' not found /application/controllers/Ueberblick.php 4

I  read:

• MY_Controller not found
  
• Class Private_Controller not found on linux, but works fine on windows
  
• Another My_Controller not found problem ... but this one is a bit different !
  
• Class MY_Controller not found
  

in this Forum and still have no idea what's wrong.

My MY_Controller is prefixed with "Main_". Thats how it is written in the config file, and thats exactly what the controller-file in application/core is named: Main_controller.php

Yes, with a lowercase c.

And I have two controllers extending the class and in both files the classes extend Main_controller. I doublechecked it several times.

So, what else can cause this error? Any help is kindly appreciated!

Raschid