have you tried it on a tv? if you can show what it does on a tv i may be able to help more. showing through a capture card will give different confused results for every different capture card, however if you put it onto a crt tv, ill more likely be able to say whats happening.
it could be outputting ntsc50Hz or something dumb like that, as most capture cards wont see that as a real format.
also, does it say genesis or megadrive on it? because remember all non-asian megadrives are pal, and all genesis consoles are ntsc.
can you link me to somewhere where i can actually see what console you are talking about? i ouldnt find another thread referring to it.