Fatal error: Cannot redeclare class ci_exceptions

[eluser]Andreas Vandenbussche[/eluser]
There was an error in the autoload.php file I guess, I started one from a new CI download and added the librarys one by one and it works now..
in fact it doesn't really work, I'm still getting some errors but I guess I'll figure it out.
If you have any ideas how I can get rid of this error:

Code:

A PHP Error was encountered

Severity: Notice

Message: Undefined property: router

Filename: libraries/MY_Controller.php

Line Number: 40

Thanks in advance!