That 'heel' says the author, He Qinglian, is composed of a number of contradictions. First that China could never have been both a cheap source of labour for the global capitalists as well as a huge consumer market. "Among the 1.3 billion Chinese people, approximately 800 million have, accordingly, no buying power".
The other great attractions for the world's large transnational corporations, those that settled their manufacturing operations in the Special Economic Zones in China, has been the appeal of cheap land, low environmental costs for their operations as well as the ready availability of cheap energy.
However, the quantity of cheap land is withering fast as land costs escalate and, in terms of the low environmental costs, China's outspoken deputy minister of China's environmental protection agency declared that the Chinese economic miracle will end soon. In 2004 Pan Yue said this was "because the environment can no longer keep pace."
In the energy sector China's crude oil consumption in the last few years "is going up by 5.77 per cent per year. During the same period, China's domestic oil supplies have only been increasing 1.67 per cent per year. In 1993, China...became a net importer of oil."  In January this year it was reported that "China is aiming to increase its coal production by about 30 per cent by 2015 to meet its energy needs...in a move likely to fuel concerns over global warming." 
The only sustained bargaining chip that China appears to still have going for it is the continued availability of cheap labour. But there are many more individuals willing to work for low wages elsewhere when global employment opportunities are few and far between.
Whichever way one looks at the problems in China's economy they look very much like those of the world economy in general:
“The biggest problem in China’s economy is that the growth is unstable, imbalanced, uncoordinated and unsustainable.” Wen Jiabao, China’s premier in 2007. 
 The Last Empire: China's Pollution Problem Goes Global
Can the world survive China's headlong rush to emulate the American way of life?
Jacques Leslie. December 10 , 2007. MotherJones.com
 'China's economic Achilles' heel' by He Qinglian. Epoch Times, October 9-22, 2009. Page 16.
 China to increase coal output by 30pc
9/01/2009 1:00:00 AM
 The China Puzzle by Bob Dinetz
By DAVID LEONHARDT
Published: May 13, 2009