[TYPO3] strange upload behavior

[Rob De Vries]

hey listers,


If my client upload an image (using filelist)  then he sees his images 
in the backend. But when he tryes to use this image (for ex. in a news 
article, he gets an "invalid file" and no images are displayed on the 
website.
When I do the same (using his account) all works fine.
Also if he uses an images I have uploaded he gets the same errors.

Someone else have encountered this same strange behaviour?

tnx
Rob