iphone 4 video play back issue

[kp7qc]

Hi everyone, I ran into a little problem over the weekend and I'm not sure it was me or something else that caused it. I have converted 4 .avi files to mp4 (iphone format) with Xlinksoft video converter. I am able to import the mp4 to itune and play it without any issue. I'm able to sync it with my iphone 4 without any issues. when I try to play it on my iphone 2 out of the 4 video skips at certain point then I lose the audio but the video still plays on. If I pause it and play again it would continue playing with audio and video. If I go back to the same trouble spot it skips again and plays without sound. I’ve re-sync with my itune a few times with the same problem and each time the video skips at a different time. Has anyone experience this issue before? Thanks