Due to a previous change in the shuttle manifest, Soyuz TMA-11’s October arrival ultimately conflicts with STS-122, causing Discovery’s launch to move to November, pushing STS-123 with Endeavour into 2008. Discovery’s return to action was set for October 17 with STS-122, but has now been pushed back to November 5. STS-123 – Endeavour’s second flight since coming out of her Major Modification Period – was set to take place on December 8, but now moves into 2008, with a new NET (No Earlier Than) date of January 17.
Source: NasaSpaceFlight.com