That's what it would be supposed to, but it does not.. :( So the script is correct?! Could you imagine another reason for this error? (There are no repeating images in my data folder which could have been a reason..)
Nevertheless, thanks a lot for your help.
The only reason I can think of is that your script contains a mistake. It is extremely unlikely that there is something wrong with 'noreplace' if applied as discussed previously in this thread.
Thank you, Dave.