Problem with custom images

[penjuto]

Hello, we have a problem on our plesk control panel, since some months ago. Custom images, such as header logo and custom buttons icons are not loaded into the web administration panel. That is, it's not loading the images uploaded by us.
Here you have a screenshot: http://img163.imageshack.us/img163/1800/screenshottm.png
We have a plesk 8.6.0.5 on windows.
Thank you very much.