We are puzzled why the graphic companies haven't just said the delay partially caused by shortage of DDR 3 memory. I don’t think they are afraid of the memory guys, are they?More info at The Inquirer
ATI is, however, openly saying to its partners that it still has shortages of X800 cards because it's not that easy to get desired speed of the memory. But it is keeping that information quiet to the press. We still don’t know why. Aren't we valued partners too?
We can confirm that the Greens - Nvidia - can get a satisfactory number of cores to run at GT and Ultra speeds but still you don't see many of these products sitting on shelves waiting for hard working consumers to shell out the appropriate amount of dosh.
Short-supply of GDDR3 causes shortage of high-end graphics cards

Rumours are spreading that delays of high-end graphics cards are being heavily affected by a shortage of GDD 3 memory. This is one of the reasons why the Radeon X800XT PE and GeForce 6800 Ultra are barely available.