I've studied a fair amount of Communist-bloc history and have noticed the following trend:
Sovietologists seem to blame the split on the diplomatic failures of the Soviet government: that Khrushchev's eccentricity, pettiness, and rather poorly disguised racism, as well as some other qualities shared by those in his clique, pushed away the Chinese as an ally
Whilst Sinologists tend to do the same thing for Mao Zedong: that Mao's craziness, irrationality, and obsessiveness pushed away the Soviets as a valuable ally.
So, whose fault was it?
From what I've read it seems relations began to weaken when China requested Soviet assistance in building a Chinese nuclear program. Khruschev asked Mao why he insisted on having this, and Mao basically told him he wanted to eventually have a nuclear arsenal and use it immediately against the US. For this reason, the Soviets did indeed help the Chinese but the information on building nuclear weapons they gave them was intentionally confusing and somewhat innacurate so that China would spend too much time and money and end up giving up on the whole thing or have a weapon after Mao (who Khruschev claimed was insane) was dead. China realized the amount of distrust coming from the Soviets and just did its own thing after that.