#18. "RE: D800 images can't be used with just upgraded LR 4" In response to In response to 17
I approached this problem with the knowledge that Adobe uses many shared libraries across their software products. With this knowledge I googled for a camera raw upgrade, found a beta version of an upgrade that will expire in April and it fixed it for LR3. LR is new for me and I have not bothered with trying out LR4 until the upgrade arrives from Adobe. I bought LR3 the day before LR3 was released and they could not give me a downloadable upgrade for free.
I think I saw a link after a quick google today that indicated that the D800 will be supported in the first dot release of LR4. Maybe you should try different Raw formats to see if you have better luck. Eg 12/14 bit, compressed/uncompressed. If some are getting it to work, this might be worth exploring. Also check out the Adobe support forums and product pages.