I have one CF that works perfectly ( Kingston 133x 8GB ultimate) and three (SanDisk Extreem IV 8GB, Lexar WA 80x 1GB, Lexar WA 40x 1GB) that are not recognized by the OS. I have tried various drivers including most up to date for the JMicron JMB363 and also the X58/ICH10R on my EVGA X58 MB. Upgrading from Vista 64 to Win 7 64 has not cleared the problem. Interestingly the BIOS sees all cards, and all 4 cards work in my Nikon D700 and D2x as well as USB CF adapters. I did an RMA with Addonucs and the unit they sent me as a replacement had the asme symptoms.
For the CF that works..it shows up in disk management with a drive letter assigned. Hot swapping works too as well as file transfers.
The other three do not show up in disk management although they do show up in boot up, and are assigned HDD0: and in the BIOS list of drives to boot from SCSI-3 ..ie JMB363 driver must see them while OS does not.
I'll try reloading drivers again since I have not tried that since the win 7 update.