I need help (keyboard input problem)

I'm suffering greatly from a very strange and annoying glitch. It's not cool or exciting, it's just a pain. Basically, while playing DKC2 on ZSNES, I've found that for some reason, I can't jump while running right (>). It works fine when I'm going left, but conveniently, most levels don't go that way. In short, I can't get run-ups for large gaps, carry barrels to high places or across gaps and I can't even beat Kleever without Dixie's glide. Does anyone know what the problem might be and how to fix it?