It doesn't recognize the hard drive I used for Time Machine backups

So, I just got a new MacBook Pro a few days ago and I set it up and everything but I opt'ed not to do a transfer from the Time Machine backup I had of my old Macbook during the setup.

A day later I connected the external drive I use for Time Machine on my MB, thinking I could use Migration Assistant to transfer some files, but my new MBP didn't pick the drive up, and I don't have a firewire 800/400 cable so I left it.

Now, when I connect the external Time Machine drive back to my Macbook, it doesn't even recognize that anything was connected, no icon pops up on the desktop, nothing shows in Disk Utility...

How do I fix this?!

Right now my Firewire 800 is connected to my wifes iMac while my MBP is away. I used SuperDuper for the back up and assumed erroneously that booting off the current back up all would be the same. Not so, it is bit like having the Logic board replaced as some items rely on the MAC. So far 3 or 4 settings have had to be reset back to how i had them. Time Machine will recognise the MAC of your new MBP so i would guess you are going to have to set it up again in Sys Prefs.

If I set it up again won't I lose the 6+ months of backups on the external?

And my problem is that my MB doesn't even see that an external drive is even connected, nothing shows up...

I did a search just now and found that you can browse other Time Machine backups by ctrl-click on the TM icon on the Dock...

So I connected the drive to my new MBP... again nothing showed up in Finder so I tried ctrl-clicking the icon on the dock... nothing showed up...

Does this mean the drive is dead?

It worked perfectly on my MB just the day before I first connected it to the new MBP...

Okay, I fixed it....

Was starting to freak out a bit because I've been trying to fix it for over 30mins now...

Apparently the USB cable connected to the back of the drive was a bit loose, but I never noticed because when I plug the cable into either my MB or my MBP's USB port the drive would light up as normal.

Thinking back I really should have physically checked the external drive and the cable... though since the light on the front of the drive lit up as it normally did I didn't think to do so.

Now I feel both relieved and stupid...