Xbox Controller problem, walks backwards slowly.

[FeeMort]

Basically, my character runs around fine, until I hold down and then it walks instead. I've tried configuring joy.cpl to be super-sensitive (by only pressing the corners slightly instead of all the way, so then it thinks i'm pressing it all the way when in reality I'm only pressing it a tiny amount) and that doesn't work. Weirdly, it only affects a few games.