Okay, I was investigating this problem a little further. In the meantime I did upgrade to the 27/08/2007.
When I hit apply, than the filename will be changed, but than the old filename will display in the lower field. If you press than okay, it will change the new filename to the old one that is display there.
So apply and okay will change the filename, but after hitting apply the old filename will insert there.
Please conact me, if you need more information on this.