So, first of all, to say that China was "subjugated" by Japan isn't quite right, because although parts of China were certainly placed under heavy, brutal Japanese control, China was far too big for Japanese forces to conquer the whole thing. In that way it presented a similar dilemma for Japan as the USSR did for Nazi Germany. But more importantly, China did not become a communist state until four years after WWII. A civil war between the non-communist Kuomintang forces (led by Chiang Kai-Shek) and the communist forces (led by Mao Tse-Tung) had been raging prior to the Japanese incursions. Mao and Chiang actually declared a truce to deal with the Japanese. But as soon as WWII ended, the civil war was back on.

Mao's forces won in 1949 when Chiang retreated to Taiwan, where he set up a non-communist government (today officially known as the Republic of China). But Soviet-Chinese relations were very different at this point than what you saw in Eastern Europe after WWII. First of all, most Eastern European nations were under de facto Soviet control in 1945 due to the heavy Red Army presence there. That wasn't true in China. Secondly, those nations had to be rebuilt, and the heavy Soviet presence made it easier for Moscow to seize control and establish puppet governments. Third, despite China's weakened state, it would certainly not have been a pushover for Stalin, in large measure because in Mao, China already had its own charismatic leader who commanded broad loyalty and an efficient military. Fourth, (and I admit this is based on a very particular interpretation of Soviet postwar policy that continues to be hotly debated), Stalin was primarily concerned with establishing Russian security against any future invasions from Europe, so that's where his focus was. George Kennan, an American diplomat, accurately described the postwar USSR as opportunistic - it would seize countries when conditions favored it, but it wouldn't start another major war to do so. China was too big and too complex for him to try to establish direct control.

Now, all of this isn't to say that China wasn't on Stalin's mind, or that he never tried to exercise any control over Chinese affairs. It certainly was, and he certainly did. But up until Stalin's death the relationship was a warm one, with the USSR and China seemingly presenting a common ideological front against western capitalism. The two nations were staunch allies from 1949 through 1953, when Stalin died. At the same time, that alliance was mostly dominated by Russia. Russian officials were going to China to advise them on how to develop as a communist nation, for instance, but Moscow wasn't listening to Chinese officials' advice on that topic. The alliance continued after Khrushchev took over, but cracks began to appear in the edifice after Khrushchev delivered a speech harshly critical of Stalinism in 1956. After that, ideological debates and poor personal relationships between Russian and Chinese officials started to deepen the gap. As China became more powerful, it wanted to strike its own course rather than listen to Russia any more. Mao wanted to develop China into a purely communist nation his way, not Russia's or anyone else's way, and he began to isolate China from the rest of the world. By 1960 the two nations had begun to split apart for good, and the "Sino-Soviet Split" became final shortly thereafter.

EDIT: small fixes.

Ultimately, this comes down to the fact that the communist cause was secondary to the nationalist cause on both sides of the border. Communism was temporary, nation-states are much longer lasting.

Take a look at a contemporary map. Yes, the USSR and China share a very long border, but the centers of political gravity in the USSR and PRC were thousands of miles apart. Most people in China live in the East (where almost almost political power is concentrated), and most of the USSR (and almost all political power) lived in the west of the country. When you think about where the political centers of powers are, you realize that Beijing and Moscow are more than 3500 miles away, and the land between them is sparsely populated and underdeveloped. This means that a lot of the cultural and historical ties that existed between say, Russians and Estonians, for example, never really existed between Russians and Chinese people. Chinese history and Russian history simply don't have a lot of overlap.

Historically, the is the master of its domain, and that domain is the East Asian Pacific Coast. China and Chinese people have close historic ties with the Japanese, Koreans, Vietnamese, etc, and China has historically been the senior partner in all of these relationships. As Mao and Zhou were moving China out of the century of humiliation, the Communist mission was intricately tied with a Chinese nationalist position, which was centered around restoring China to its historic position of power. This position did not allow for China to be a junior or subservient partner to the Soviets.

There were other, more tangible issues. One of these was the Korean War. Mao felt that the Kremlin had tricked him into getting involved in Korea, and had not provided the necessary aid, forcing China to put up the manpower and money required to fight a war that resulted in pretty much nothing.

Another is the Taiwan issue. The PRC and the ROC engaged in shelling throughout this time period, leading to fears that a major war could break out, with the US backing the ROC and the Soviets backing the PRC. The Soviets did not like the fact that they were essentially being manipulated into extending the nuclear shield to islands like Quemoy and Matsu, which were simply not priorities in the Kremlin. To the Chinese though, Taiwan was (and remains) at the top of the list of priorities. Again, when you look closely you find divergent national interests.

Another was the Sino-India War and the Cuban Missile Crisis. The Chinese and the Soviets were both very mad at each other over this. In particular, the Soviets felt that the Chinese had undermined their position by attacking India and broadcasting the fault-lines in the Communist and pro-Communist world. Again though, you'll see that this is an example of the issues that China had balancing out the communist mission and the Chinese national mission.

There are plenty of other things worth mentioning as well, like the personal distrust that Mao had for Stalin and Khrushchev, but when it comes down to it, all of those could have been worked through if there was the political will to do so. There wasn't, because the Chinese were not interested in developing the type of partnership with the Soviets that the Soviets wanted with the Chinese.

/u/ThinMountainAir more directly answers your question though, my answer is more like the sequel to his.