B&W Tv-Out with FX5200 (but it works with Gf4 MX)

hello!

I have a problem with my recently purchased laptop Inspiron 8600 of
Dell. It contains a Geforce FX 5200 64 Mb with the latest drivers
installed. As you can guess, I have a black and white picture on my
TV. The -weird- thing is that it perfectly worked with another card, a
Gf4 MX 440 (MSI), I had colors and a good picture quality. The
connection is the same for both cards : from the S-Video plug on the
card to the composite input on my TV (I have one S-Video to Composite
cable). I read a lot of stuff about this problem but it's always
saying that the TV is not able to decode the signal. That doesn't seem
to be the case with my TV (I live in Switzerland, it's PAL)

Why did it work with the cheap GF4 and not the FX ? Are there
differences even in the S-Video standard ? Is the S-Video signal from
the laptop corrupted or too weak ?

This is really strange.. I also tried some S-Video to SCART adapter,
still black and white with the FX. I tried a lot of settings, both on
the software side and hardware (AV-1, AV-2, TV settings..). If anyone
has some hints about that issue, I would be very happy. Thanks for
reading this