Well not all is right as rain, my old Rosewill RC-605 uses Silicon Image drivers and won’t run on Snow Leopard, so I got a $20 OWC ExpressCard eSATA and it sort of works, but the driver crashes and the drive disappears on the latest Snow Leopard. How sad.
Sonnet’s version of the Sil3132 driver works with the Rosewill RC-605 card in 10.6.1.
Try this: install the driver, repair permissions, shut down (completely — don’t restart), then plug in the card and reboot. After you log in, turn on your connected drives, they should mount. If not, restart again with the drives turned on. YMMV, but that’s how I got it to work. It’s fully operable, plug-and-play now.