Macbook Pro (late 2011) won't recognize external drive

Hi all,

Looking for some advice. My new Macbook Pro (late 2011, running Lion) won't recognize my external hard drive. The drive is an ioSafe "rugged portable", which runs off USB (and doens't plug into the wall). It has a capacity of 750GB, and I would like to use as a Time Machine for backing up.

The drive works fine, and I've run numerous diagnostics when connected to an old ThinkPad. However, whenever I connect to my MBP, the drive just makes a spinning noise and gives no indication of being read by the machine. It does not appear in Disk Utility or in System Profiler.

I spent last night reformatting on the PC, and it shows as a blank drive on my ThinkPad. This morning, it still wouldn't read on the MBP. I did some research and it sounds like others have had a similar problem recently, so on a whim I brought it over to my old iMac, which is still running Snow Leopard. The iMac recognized the drive immediately, and prompted to use as a Time Machine.

I formatted the drive on the iMac to use the recommended Apple system (journaled), although for some reason it made me partition it into two. But it worked and is recognized by the iMac. Brought it over to the MBP, and it still will not recognize.

I've tried both USB ports, neither seems to work. Each works with other types of peripherals and other external hard drives. But if you read up on the "rugged portable", you'll understand why I want to use that as my primary backup.

• Is this an issue with my MBP, or an issue with Lion?
• Is there a method to resolve the issue?

Thank you in advance!

*Worth noting, I also ran diagnostics on the ioSafe from the working iMac, and everything checked out.