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My 133x cards in my 12mp D300 don't take 1-2 seconds to come up, so it's not the read speed of those cards.
However, I did have one Transcend card that I eventually diagnosed as bad. It seemed to hold data fine, but it was far slower than my other cards of the same brand/speed/size, and would cause my image review to be slow coming up, slow flipping from image to image, etc. I don't know how many cards you have tried - if it's more than a couple, that's probably not the cause, just thought I'd throw it out there.