external hard drive won't show up on macbook!?!?!

I have had an external hard drive (time machine) for my mac for over a year and the other day I was using a not so good USB cable and it kept ejecting my hard drive from my computer. When I tried to plug it back in, it didn't show up! I have had this issue before with another hard drive and the same USB cable thing happened and someone helped me but I can't remember what I had to do!
When I go into Disk Utility, my drive shows up and it all appears normal except under S.M.A.R.T Status it says 'Not Supported'. Also the Repair disk option is greyed out as well as all of the other options on that page!

Please help me!!!

Did you try using a new USB cable? They're inexpensive items which can be purchased at most stores which sell computer accessories.

And yes, SMART is not supported for external hard drives. As far as Disk Utility not allowing repairs on the drive... that could be because the drive is not being mounted correctly. Bad USB cable?

Thanks for replying
Yeah, I did try it with a new USB and it still only shows up in disk utility.
Ohh thanks about the S.M.A.R.T thing, I thought that was the problem!
I just went into disk utility then and clicked on the drive and went to info and this is what came up:

Name : WD 3200BEV External Media
Type : Disk

Partition Map Scheme : Apple Partition Map
Disk Identifier : disk2
Media Name : WD 3200BEV External Media
Media Type : Generic
Connection Bus : USB
Device Tree : /PCI0/EHC1@1D,7/@4:0
Writable : Yes
Ejectable : Yes
Mac OS 9 Drivers Installed : No
Location : External
Total Capacity : 298.1 GB (320,072,933,376 Bytes)
S.M.A.R.T. Status : Not Supported
Disk Number : 2
Partition Number : 0

is something not right here?

Everything reported on the drive is correct. I have the same Western Digital drive as that installed in an older MacBook.

What I suggest is to try plugging the drive into another computer, it can even be a PC, to see if it's recognized. If it's not or you receive an error, the drive may be defective and might have to be replaced. Since it was used for TM you won't actually lose any data but you'll have to start the backup all over again from a new drive.

Can I try restoring the drive and then see if it works? If so, what's the best way to do that? It was recongnised in the control pannel of a PC, but it didn't come up under My Computer..

You won't be able to restore the drive if it can't be accessed. And if it doesn't show up in "My Computer" it can't be accessed from a command prompt either. I think your drive has seen better days.