acomdata external hard drive problem...

ok im running a powermac g5 with panther.
i am transferring a good bit of skate footage from my internal HD to my new external hard drive.
all of a sudden in the middle of the transfer it tells me that i have not put it away properly and by doing so i may have lost some files. so im like okay and click ok. (its very important to realize that i did not do anything and was sitting AWAY from the computer)

and now the external is gone... my computer isnt recognizing it, still plugged in.
so im like alright
and unplug it.

i try to plug it back in, and no dice... try to restart and see if it will mount... no dice...
help?

EDIT: ****... sorry guys wrong forum. hah and first post. if someone could still answer that would be great.