Scenario

We upload images via Multiple-File-Uploader in the magento backend. The upload went on the first look well, the image is shown in the table under the other images. As I hopefully wrote here the images are loaded from the server in full size, but especally FROM THE server. This means the files were saved on the server.

Logout after submitting the form

After submitting the form, I saw the admin login. I didn't check what exactly happens here. Thanks to google I found the answer in the magento forum:

suhosin.session.cryptua = off 

This setting is in the standard .htaccess with this comment:

# disable user agent verification to not break multiple image upload

I have really NO idea, why everything works, when I turn on this option, but afterwards I wasn't longer logged out after uploading an image. So just change the setting to:

suhosin.session.cryptua = on