Copy to in Explorer not working with Digital Camera

Hello,

I have a Canon Digital Camera which is recognized by Windows XP als a
Digital Still Camera and displayed under My Computer as a Camera
(without drive letter). Thumbnails are displayed, and Windows Picture
and Fax Viewer openes the Images on the Camera.

But I can't copy the pictures using the Explorer: Neither right click
on a picture and "Copy to folder" nor Windows Copy / Paste work (simply
nothing happens). Whereas the Wizard works normally. A double click on
movies on the camera brings me directly to My Pictures folder - but
without copying or displaying the movie.

This has been working perfectly before and stopped suddenly...

Thanks in advance,
André Christ