Actually the issue is probably a bit of both. And the problem also has to do with tv screens not being square pixel. So the aspect ratio on tv is actually not the same as on your computer.
since the tc screen only does 720 px wide… a lot of video cards with tv out will try to send a 800 x 600 type signal to it… which works, but not too great. Try setting your monitor/tv out to that though, it should make it easier for your laptop since it won’t have to resqueeze the image.
You should not be able to even set the refresh rate for your laptops tv output. tv outs have a default refresh rate, though setting it to 60 may make everything a bit easier for the video card, especially if it doesn’t have it’s own ram.
Oh and please tell me your laptop has a line out for sound so you don’t have to use the headphone out. Headphone out can be used but since it’s amplified, it’s not a wise choice and if you happen to have the sound to loud you could blow your tv’s imputs.
I’ve had the best results going from cinch (you know the yellow cinch plug for video) to scart. I don’t think S-video has exactly the same aspect ratio as a tv screen either. So in your case your squeezing your monitor out into s-video and then your tv tries to make it intelligible by redoing it again… no wonder you have phase issues.