UE46D6500 wont fast forward certain files

[gffb]

Hi There,

I have a 3D Samsung UE46D6500 TV, I have loads of video files stored on a server and connected to my TV via my network. I use Twonky on my media server to play the files on my Samsung TV. Now here is the issue. Some MP4 allow me to fast forward using the samsung remote and others do not. I am not sure why this is as both files seem to be the same?

Is there any reason my some MP4 files will aloow me to fast farward (time search) while other MP4 files wont.

Thanks for your help.