Cannot play mp4 (h264) video file

[HeavyMetal]

...cause the picture is all gray, as if the file were damaged. However, after some time video appears and shows ok, but once you use skip (forward or rewind the file) picture breaks again.
Same problem with few files.
Video codec is mp4 h264, audio - AAC
Tried different settings like changing video output, postrpocessing, allowing to play bad indexed files etc. - nothing works...
System is p4 Core Duo (8400), ATI HD 4870.
What can be the cause?
Thanks

[HeavyMetal]

Many views, but not a single reply to my post.
And the problem remains, no matter what setings I use and no matter which version of MPlayer it is (just downloaded the newest one - 32674 - but it didn''t work either). Screen is gray as if the picture is broken, after some time it gets back to normal but breaks again if the file is skipped
No one has an idea what's going on?..

[rvm]

Have you tried changing the correct pts option in preferences -> advanced?

Or change the demuxer.

[HeavyMetal]

Thanks.
Correct pts didn't work, but changing demuxer did. However, only .mov demuxer worked, others did not, and skip is kind of weird with that .mov demuxer, but it's better than nothing anyway
Thanks again