Can't attach files
 

Vbulletin 5 beta26
PHP 5.3.20 Safe Mode ON

I can't attach files.
When I create a new topic or reply to an existing one, I use the advanced tab to upload an attachment, I select “upload”, I choose the files to attach (images or other), then I click on “start upload”: when the progress bar reaches 100% nothing happens (the files disappear from the windows).

If I use the Shares Photos tab, I can upload images without problems.

If I go in AdminCP -> Maintenance -> Diagnostics -> Upload and try to upload a file (image or other) the result says “No errors occurred while opening the uploaded file for reading.”

Any ideas?