I think my guess was accurate; Obama came to Beijing to discuss the coupling of the RMB to the USD; not to ask the Chinese to break it, but to KEEP it. The RMB is getting valued higher and higher, and that's helping to keep the USD up (via the peg).
When the Chinese unpeg the RMB from the USD (even for a 10% correction), the RMB will gain against other currencies, and the USD will plunge even further against those same other currencies. Right now, the peg is one of the solid things keeping the USD from plunging like a rock in deep water...