|I'm having the EXACT same problem you're describing, to the t.|
I have a 500GB SATA seagate barracuda, 7200.9
No idea what's wrong with this thing, it's not a boot drive, but I have an immense amount of important data on it. This f'ing blows.
Let me know if you discover something, I've contacted two data recovery companies to have the disks scraped of everything.
here's my awesome signature