Help!! Macbook can't detect external hard disk!

My Macbook used to be able to detect my external hard disk all the time. However recently it doesn't detect the external hard disk most of the time even though the light on my external hard disk is lit up and I can hear the whirring sound. Now whenever I plug it, it is only detected 1/20 times. And even so, it ejects by itself after a while. Pls advice, thanks a heap!

Have you tried to mount that particular hard disk on another computer? Have you tried to mount another hard disk on that same computer that won't recognize the drive you're having difficulty with?

Regards.

Exactly the same problem! It was working well then no detection of my hard drive, or once in a while! However this hard drive works perfectly with windows.
Have you found a way to fix it?

I fixed my similar problem by going to disk utility, verifying, then repairing.