Sudden drop in Read Speeds - PLEASE HELP

Sorry, first time forum post and not the best when it comes to computer hardware.

I have a WD 2TB MyBook used on my MacMini running Snow Leopard. It is full with all my family photos and video.

It has been working great up till yesterday and although I can still access the drive and see what is on it is is incredibly slow and results in a failure to read the files often. I can no longer view the video off it and iPhoto will freezes when it tries to access the drive. It seems to be a lot hotter than my other 1TB drive. I have tried swapping it from Firewire to USB with no improvement. 

I have left it unplugged and the retried with no luck. I am a little lost now. Any ideas. Is my drive faulty and if I need a new one how might I get the data off it?

Any help will be greatly appreciated.