Same problem here also: G-Speed Studio XL disconnecting while computer is asleep. Happened rarely before but with latest update, I'm getting 10+ messages each time I log back into computer if I've been away for more than 4 hours. If gone just 2 hours, I've got 5-6 messages. It's ridiculous.
Curiously, I also have a G-RAID drive that never disconnects.
Both drives are Mac OS Extended Journaled.
When I try to eject the Studio XL, it's cannot eject and must be forced.