I want to copy one album to another collection ... there is simply no button for this in the manager. So I tried copying the actual files on the server ...

for example all files in
/components/com_expose/img/alb_11 to /components/com_expose/img/alb_43
If you do this manually you need to edit the xml file for album 43 as well /components/com_expose/xml/alb_43.xml and replace all references to alb_11 into alb_43... still following me ?

Anyway, this works, however there must be something else since the copied fotos can't be moved out or edited from the manager ??
ANyone any idea ???

You have to download the files and manually edit the xml.