External drive not readable after Yosemite update

I'm getting "The disk you inserted was not readable by this computer." on both of my external drives that were plugged in while my computer updated to Yosemite. Both are Seagate Free Agent Goflex; one uses Thunderbolt and the other is Firewire...

Any ideas how to recover the data? I plugged it into my wife's macbook that hadn't been updated yet and I'm getting the same result.

Ok so I had my TB drive and my FW drive switched. I moved the drives to different adapters. (The Seagate drives can be hot swappable with onto their SATA adapters)

I've since moved them back and it seems to be working fine again... thank ****** christ.