Seagate External HD (GoFlex) Crashes Macs Situation: My most important external Hard drive is crashing my computers. It had my time machine backups and random files stored. I've tried it on my iMac and Macbook Pro. It may be worth noting I installed Parallels recently. 

Does anyone have any ideas or solutions? I was about to open it up. The fact that it shuts the computers down makes me think it isn't necessarily a read/write failure?

Specs:

Seagate FreeAgent GoFlex 9ZF2N5-502

iMac
3.4GHz Intel Core i7
4GB 1333 MHz DDR3
Software  OS X 10.8.5 (12F2560)

Tried so far:
-Using the closest port to the power. 
-Changing USB cables
I had this problem on many Mac OS X and OS X versions with different external hardware devices (even iPhone!). Installing the last version of OS X was the only working solution.
Even with upgrading the OS X, problems remain.