nVidia basically has the same problem as ATI had (and still do) when the HD5XXX series came out. The chips are manufactured in the 40nm manufacturing process my TSMC and there are still yield problems with it. As far as I know the next big shipment of Fermi-chips is going to be around the beginning of May. So If you really want one you should just keep looking everywhere
It'll get even worse when they "try" 28nm.
Oh and btw. Makes no sense to get one. Your Q9400 won't be able to deal with it anyways. If you want something as high end as a GTX480 or a HD5870, you'll need an i7. Preferably overclocked aswell