I have a Macbook Pro that had a 320GB hard drive. I bought a new 1TB hard drive. I connected the 1TB HD via USB (had a SATA->USB connector) and used Carbon Copy Cloner to clone the old HD to the new one.
Clone said it was successful.
I switched out the Hard Drives and now I get a flashing question mark. I switched back to the old one and it booted back.
Just to test it, I connected the 1TB drive again via USB, click System Prefs, Start Up Disks, and selected the 1TB (which was connected via usb) and the system booted up fine.
I then took the 320 GB hd out again and connected the 1TB again via SATA and again I get the flashing question mark.
I hold down Option to bring up the Start Up Manager and no disks appear.
This is really puzzling me.