PS3 can't read video from MyBook World Edition 1TO


First of all, excuse my english, it’s not my first language.

I’ve got a MyBook World Edition 1TO.

I can access it on my local network. UPNP is available. My PS3 see the MyBook World Ediion, it can read music and pictures.

I also can see movies, but I can’t watch it !

When I launch the movie, the PS3 tells me that PS3 can’t read it.

But when I put this movies on an USB device and plug it on my PS3, PS3 can read it !

Have you got a solution ? I bought the MyBook World Edition to share my movies with my PS3…

PS3 : Fat, 80go. Wifi access to my network

Computers : Macintosh on OS X 10.5

What version of the software is the PS3?