Attach button doesn't work

Over the past weeks I have performed several Drupal 5.1 installations on Windows XP (SP2) and Windows Server 2003 (SP1/SP2). I enabled file upload from the "Core - Optional" module list. I use the TinyMCE WYSIWYG editor. I have set the file system's download method to either public or private, but this doesn't seem to affect the behavior of the "Attach" button.

On most of the installs I never get the "Attach" button to work.

• Logging in as a regular user, I can only upload one single file if I do not click on the "Attach" button and directly submit the node I am editing and attaching a file to.
• If I click the "Attach" button on a node I am editing, the file is uploaded to the PHP temp directory (by default: C:\Documents and Settings\mobile\Local Settings\Temp\PHP\upload but saved as C:\DOCUME~1\mobile\LOCALS~1\Temp\php\upload), and is given a temporary name (e.g., "tmp39.tmp"), and it is shown as an attachment in the "File attachments" table... until I dare to type either "submit" or "preview". Then the attachments are not transferred to the Drupal environment (the +/files/+ directory on my environment).

It looks like somewhere in the process of uploading there's state information that is gone when the AJAX Upload magic is invoked.

All help is greatly appreciated!

Best regards,

Olivier