Android sdcard appears empty to Windows? I have a Archos Cobalt tablet.

The external micro sdcard appears empty to the tablet and to the pc when the tablet is attached via USB, debugging on.
I have used app2sd to move apps to the sdcard. Without the card in they don't work so it must have moved them but it still appears as blank to the tablet and pc?

The contents of the tablets internal disk appear ok on both the tablet and in Windows so whats the difference?

I have also tried removing the card and plugging it in again.
I've done some research and it seems to be an oddity of the tablet. 

When you do 'move to sd' whats happening is its moving data to another part of the -internal- sdcard. You can't move apps to the external one

e.g.

http://yatse.leetzone.org/redmine/boards/2/topics/259#.UTfGXxyeN8E

thanks anyway