We have found a solution in the EnCase forums. Apparently EnCase (I am not sure if version 6 fixes this) does not recognize the GUID partition table used in newer Macs with EFI. Following is a manual fix from Bill Siebert in the EnCase forums to get the filesystem to show:

1) Search the disk for "HFS"
2) Wait a few minutes and refresh the search hits
3) In the search hits, find the HFS at the top of the list and click on it
4) Switch to disk view where the HFS keyword was found
5) Move back 2 sectors, right click, select Add Partition, choose HFS+
6) Let the file systems rebuild
7) VOILA! The The folders and files will appear

Note: some people have reported having to use the second search hit, rather than the first.

Thanks Harky. We could always use some good additions to the Forensics Board, even if you do answer your own question. 

Don