plopje,
In regards to playing the files, I do not have the Archos model you are testing, but on all the Removable Drive players I have, if I double click the file, it begins to play. Also, if I right click and select "Play" this works as well. Could you try the right click and see if it works for you or is that what you meant by "select in right pane...".
In regards to checking the folder attributes, you are right, it will not work to send me the folder. Would you mind emailing me at steve @ jriver.com. I would like to send you a modified Plug-in that will show me the information I need for the folder attributes. If you wouldn't mind installing it and telling me what you see, I should be able to resolve this.
Thanks,
Steve