The disk icons & text for both internal & external disks are gone from listing in Finder[ Places section] and on Desktop. The disks are listed in Finder DEVICES section as Partitions
The physical drives do show up in Disk Utility.
I have "turned on" showing all the disks in Finder preferences.
Also just now the drive from the Windows 7 PC on my local net disappeared.
External drives connected via USB no longer POP UP on the desktop, nor do SD cards.
10.6.6 has been very stable [until now] for over 1 month.