I have tested some more.
To add insult to injury I have discovered that if I try to connect NTFS or HFS+ usb disks to the MyBook World those DO get automounted and shared over samba.
This gave me the idea that I could monitor the log file and try to examine the difference from when I insert the ext3 disk and when I insert the NTFS/HFS+ disk, and from that figure out why the ext3 disk is not mounted and shared.
First, here is the output from the ext3 disk that is not mounted:
Jun 13 17:31:11 MyBookWorld user.notice : disk at /devices/platform/oxnas-ehci.0/usb1/1-1/1-1:1.0/host4/target4:0:0/4:0:0:0
Jun 13 17:31:23 MyBookWorld daemon.info wixEvent: USB Status - USB device inserted.
Jun 13 17:31:26 MyBookWorld user.notice : ... no modules for USB Western Digital My Book
Jun 13 17:31:27 MyBookWorld user.notice : Setup usb-storage for USB product 1058/1100/175
After making sure that no other entries were coming I used the WD Web UI to safely remove the ext3 disk. Log entry not included.
Second, here is the output from the NTFS/HFS+ disk:
Jun 13 17:34:54 MyBookWorld user.notice : disk at /devices/platform/oxnas-ehci.0/usb1/1-1/1-1:1.0/host5/target5:0:0/5:0:0:0
Jun 13 17:35:10 MyBookWorld user.notice : ... no modules for USB Western Digital My Passport 070A
Jun 13 17:35:11 MyBookWorld user.notice : Setup usb-storage for USB product 1058/70a/2003
Jun 13 17:35:14 MyBookWorld daemon.info wixEvent: USB Status - USB device inserted.
There is only one difference between these log files and it is a small one. The difference is the order in which the entries are written. The ext3 disk causes the "USB device inserted" entry to appear as the second item, while the NTFS/HFS+ disk causes this entry to appear last.
This doesn't help me much as far as I can tell. Any other suggestions as to what I can try?