Banner image upload not working

[fschulze]

When I try to upload an image for a banner, it says the banner was successfully updated but no image is there. There is no error message and the database is updated with the correct dimensions of the image. If I manually copy the image to the correct folder and set the "filename" in the database, everything works. I can't find any error in any log. The permissions seem to be correct, the php fast-cgi user can write to the images folder and the parent folders are accessible. The configuration has the correct folder and the mode is set to "local".