I have heard of some people having probs with controllers running only on USB cables especially on MACs apparently after 1-2 hours something goes crazy with the power suplied to the USB ports ... I'm not really that deep into computer/ electronics, but I would in know some brands of controllers do suggest you use an power adaptor with they're controllers... In the 1d case you have no power socket, so maybe you can use one of those powered USB HUBs. Try and find someone that can lend you one just to make sure if this is not the prob., at least it's another avenue to try and solve the problem!

Z