Fixing Out of Sync Video files?

Hello All,

I’ve been converting some videos so that they play on my Ipod. In doing so, the audio falls out of sync with the image. How does this happen? Is it a result of a lack of ram/processing, or just a glitch in my software?

Is there any way to fix it without re-converting it? Can I take the audio track and (using some sort of free editing software) slide it forward or backward a few seconds?

Thanks!