i never had any probs, the theory is all similar and the practice aint too far apart either.
it certainly gives you a better idea of how what you play will effect the dynamic of your band if you can think like a bassist and a lead guitarist. and learning both from the start will put you ahead of other guys further down the line as you will have been playing and thinking like both from the beginning.
oh, and picking up on an earlier reply, the guitarist should know as much as the bassist about music, and should certainly know what notes both he and the bassist are playing.