I doubt it's the cable. I've got a 30' cable that I've used more than a few times for video feeds. There may be a problem with converting from the s-video signal to rca, and in that case a converter like rthompson80819 suggested may do the trick.
Edit: I just checked on some of the reviews for svideo to rca adapters on Amazon, and everyone that used them (much like the ones you described) said that they work perfectly....... I'll try some things with my laptop and an adapter and let you know what I find out.