It is not possible to delete files form NMT

[henk]

I have a pc where linux is running.
Ik upload files (movies) directly from my pc to NMT by usb connection
I have formated my harddisk on NMT with ext 3.

The first upload works well. I create a subdirectory and write the files in this directory.

After that I was looking to the movie I want to delete this movie and copy other movies to the same directory exactly the same way as mentioned above.

But it is not possible anymore to copy to this subdirectory or to delete the movie that is in this subdirectory!!!
It is possible to copy to the root or to other new subdirectories.

I get a message that I have no writing rights but that is not true because I am be able to copy them everywhere but not in that subdirectory

Who can help me