strange w950i problem.

I have mp3 files which are longer than usual songs, its like some class lectures. Now whenever i try to forward the file after 1 hour, it would simply skip to the next track. The file plays fine if i don't forward/rewind. I could forward it maximum till 1hour. if i forward it till 59 minutes, it plays fine till the end. i am gonna sell this fone if i dont find a solution soon 😞. do help me