Problem with m4v video format

[sagri76]

Hi,
i'm from italy (sorry for english).
I never had problems with m4v video files with video lan (0,8,6f). i watch video and ear sound.
a friend send me a m4v video and i cant open it. the bar walk very fast but no video e no sound. i tried quick time (error 2034 or similar (not compatible file)), other player, converter, etc. try to change extension with mpg, avi and mp4, but nothing (with mpg and avi, the bar walk a bit slower but no video). my friend tell he can to see it with mac with no problems.
please help
SAm