3 year old MyBook Mirror edition spontaneously unmounting

I use this as a mirrored RAID drive to back up my photos. In the last couple of days, after an episode in which I think the cat uplugged the USB cable, the drive has been occasionally spontaneously unmounting. I get the “This drive was improperly disconnected” dialogue box onscreen.

Any thoughts? Is this thing dying? It hasn’t seen heavy use, but has been plugged in for most of that time.

Thanks.

Sorry: I’m running it on a mid-2007 iMac, which is running Mac OS 10.7.4 .

Yup dying

old drive + unsafely disconnecting = data loss

backup data ASAP and consider getting another one