Problems with over-long tracks

[patlabor]

Hello everyone, i am mainly using my sansa e280 with cpchans build to listen to audio books. its just perfect with the bookmarks. yesterday i had a audiofile that was well over 90 min long and there rockbox was starting to behave stangly. near the end of the track (but still missing about 15-20min) rockbox simply skips to the next track. its not allways at the same time sometimes i can hear allmost the complete track the next time i miss the 20 minutes. when i play the track from the sansa memory under windows it works fine and plays all the way anybody has any suggestions what the could be or better how to fix it?