Undefined error when replacing image

Hi,

I want to replace the logo on dtcdredges.com (I know, not secure. This site will be removed in a while). When I want to do this, I get an unknown error. Any idea what this error means?

Can you post this screenshot with more details around. I have no clue where this could be. Also the TYPO3 Version could be helpful.

Hi Stefan,

thx for the reply. It is version TYPO3 4.5.40. And in the attachment the location of the file. When I want to replace the file, I upload the new one. If I do this, then the error appears.

Regards Bas