One should insert CF cards into the slots only when the adapter card is ejected because the interface to CF cards is ATA and ATA can only instantiate itself to the system when the adapter card is inserted. You can unmount and then remove CF cards when the adapter is inserted, but you can't plug in new ones unless you first power off and eject the adapter card.
This is a Microsoft Windows driver bug with some 64GB CF cards. Sonnet is working with Microsoft to resolve this issue. (64GB and 128GB CF cards work fine with Qio and Qio-CF in OS X.)
A partial list of cards Sonnet has tested:
Patriot Pro CF 266x 64GB/128GB card is recognized under Windows
Lexar Pro 1000x UDMA 7 64GB/128GB card reports itself as 32GB
SanDisk Extreme Pro UDMA 6 64GB/128GB card reports itself as 32GB
