First, thanks finally for Philips reply.
I have allready upgrade my router and my internet speed to 12 MB and my PC to win 7 (from XP).
Now I can watch all movie without any interrupt (1.5 hour) but once the movie ends and I want to go back to my PC share file list NO network\DLNA, all is disappear and need to setup again the network. I'm using wirleess connection.
I can't connect my PC to the TV without any device in between since I have only one port for network on the PC. (and my PC need to be connected to the internet too.)