RGB to NTSC converter PROBLEMS!

I recently got an RGB to NTSC converter from Jrok. Great guy. Anyway, I am having some trouble with it. It seems that when I first tried to hook it up to my MVS (medium board) the picture would fade out after about 3 seconds. Then the picture would stay, but it would be garbled, but only when ran through composit. It wont even recongnize the S-video out...WHICH I NEED! My friend hooked it up, and he is quite the electronics guru, but wanted to see if anybody has any ideas, we are clueless. Please dont say check the power or the carts, those arnt the problems.
-Mike