Chinese broadcasters, including CCTV Olympic and all other sports stations have taken the NBA Eastern and Western Conference Finals off the air. Websites have also been directed to shut down their live NBA streams. NBA games have been totally boycotted inside China.

No official explanation has been offered on the boycott, but rumors have been spreading over the Internet.
NBA games were originally taken off the air during the May 19-21 three-day national mourning period [for the victims of the Sichuan earthquake]. And on May 22nd, CCTV Olympic resumed its coverage of the games. So did all other local TV stations.

Then on the morning of May 23rd, CCTV Olympic canceled a live playoff broadcast and has not featured a game since. CCTV Olympic anchor Yujia said “the day before yesterday I received a note from my boss saying the live broadcast of the game had to be postponed.” The chief of CCTVs sports department later said live NBA broadcasts don't fit the nation's atmosphere after the earthquake in Sichuan.

On May 26th, Guangzhou TV halted live broadcasts and all other local stations quickly followed suit.

Websites like pplive and ppstream removed live NBA content on May 28th.

Basketball fans in China are currently unable to watch NBA games on any domestic TV channel or website.

Staff from CCTV says games will appear again in June.

Rumours:

1) The Sharon Stone incident has spread to the sports world. The government boycott has essentially washed the many years of hard work the NBA has put into China down the drain.

2) An NBA executive has been recorded as saying that after the Western Conference Final, the NBA started to encourage players to become involved in “important social issues”.

The executive has also listed a specific example. Last year, Ira Newble (formerly signed to the LA Lakers; now playing with the Cleveland Cavaliers) issued a public letter criticizing the Chinese government for being involved in the Darfur conflict. Mr. Newble's efforts eventually brought him to a Los Angeles-based group called Aid Still Required, which asked NBA players to record public-service announcements in hope of pressuring the Chinese government to consider its role in Darfur.

This is not the first time the NBA has been pushed off Chinese airwaves. In 1999, when the Americans bombed the Chinese Embassy in the former Yugoslavia, CCTV canceled all live NBA broadcasts, and instead played recorded games during the summer.
                            
Source: 新快报
A very special thanks to XQ for the translation