I'll refer you to the Asian tab on the portal for the "why's"? I think the most important “why” was the 1st contraction we've seen in the Chinese PMI survey since 2005. This happening before the Olympics definitely caught me by surprise, considering in most cases that China has the ability to make some of these number up.
The worst week however, in context, for this currency is a -0.34% move. So let's not get all hyped up about this. Re-flating the US Dollar, and deflating the Chinese Yuan is going to be a long term process.
The Yuan is currently trading at 6.84 per US Dollar, and is still up +6.7% year over year relative to it.