External drive keeps disconnecting

Hello,

Can anyone give some advice, please:

My Western Digital external drive, out of the blue, started disconnecting and also I can't send videos (or anything else) to it, as when I try it, it disconnects and will come up saying:
'the operation cannot be completed because you do not have sufficient privilege for some of the items'

God know what 'privileges' I should have

I don't know what it means and what to do
Any help greatly appreciated!

try this,
open disk utility.
select your drive from the list on the left.
click on repair disk permissions......
post back with results...

disk repair doesn't work

Thank you, Zigdog, I did try disk repair but the drive disconnects so quickly that it doesn't have time to repair!
Do you think the problem is with the macbook or with the drive?