I found a work around for my problem:
3097829181	localhost	nil	/uploadTest.1.upload	nil	
*** an UploadURLmap: Message not understood: listOfAttachments

After browsing some more code I noticed that the method listOfAttachments is
not a UploadUrlmap method,\
though an UploadSwikiAction method. So :

I replaced 
<?request map listOfAttachments?>
with
<?request map action listOfAttachments?>
in upload.html

And it works....
I you see any disadvantages, or you have a better solution : let me know...

Greetings
Frederik Vandendriessche
System Engineer, 
Electronic Business Services,   
frederik.vandendriessche at eds.com
phone ..32/0 2 711 37 83
fax ..32/0 2 711 39 47