understand why they won't accept US Bonds any more, simply because they are the world's largest holder of this paper, except maybe for the Federal Reserve themselves, who are now playing a circular swap game, with those bonds, in order to keep the Dow index ticking over.
That's not the reason, and the Fed is not playing any games. The Fed's actions have brought the US economy into something approaching economic health but prophets of doom never tire of saying they didn't. The US economy is in considerably better shape that it was in 2008, many signs of the US leaving the recession behind, such as 2.3 Million Full Time jobs being created in the last 12 months alone and 5 Million Full Time jobs being created in the last 2 years.
China has stopped pegging the yuan to the dollar directly, and is now allowing the yuan to float to a limited extent. With the yuan now responsive to the market, the belief that China was undervaluing the yuan greatly is now called into question since it is floating downward
. This is very probably due to the fact that many in economic world have begun to doubt if China's growth rate is really as high as they claim.
Your claim that China not accepting US bonds as payment for anything is supposedly a sign of the dollar's weakness is exploded. If the dollar was weak compared to the yuan, the yuan would be floating UP, not down.
As far as China buying gold, so what? Russia has been taking on gold and their economy is still a shambles, with a shrinking GDP, high inflation, and a currency that is worth less than half what it was two years ago.