Instead of my usual habit of using superduper to mirror my drive to a new computer, I just physically moved the hard drive from an older iMac to a new one. But... it now doesn't boot, getting stuck at the apple logo screen.
Since the hard drive that came with the new iMac works well, and my old drive works well when I return it to the older iMac, I conclude that there is some problem at the system/kernel level due to the different hardware. In the past I did similar things (e.g. starting a C2D machine from a Core Duo in target disk mode), so perhaps the change in architecture to the i5/i7 is too problematic?
The main point: do you know of any way to get the system to rebuild for itself the proper versions of the system components when booting? Are there certain directories that I can safely delete to make that happen?