WD MyBook 1TB stops playing avi

Hi all,

i have a WD My Book Essential 1TB (  http://www.informatique.nl/110595/wd-my-book-essential-1tb-zwart.html ) and it does some strange things since yesterday.

When i’m playing a movie (.avi) , after some random amount of time, it stops playing and my VLC-player comes back with a message saying sth like “the file isn’t readable” anymore. Also i get a windows-error and the drive disappears from the drive-list in windows. It will show up again when i reboot and all data seems to be fine. The avi is not the problem, cause i can copy it to my harddrive and watch it from there. 

Anyone knows what to do?