Thanks, guys.  I really appreciate the leads and enjoyed reading the links you sent.
I'm going to hold off on updating drive firmware.  Here's why:
I set up my DNS-343 as an FTP server, and I can see the volume and all subdirectories and files.  I can read, write, and even rename files and create directories.  But only in the FTP protocol.  So I don't think my problem is with the individual drives or with the RAID-5 logical disk.
My problem is that I just cannot connect to that volume from any PC in my home.  I've tried everything I can think of, but am "turned down" at every attempt to map a drive.
This seems very similar to a problem that another poster on this formum had.  He finally tracked his down to Zone Alarm.  I don't have zone alarm.  And anyway, I turned off my antivirus and Windows Firewall to no avail.
Any ideas?  Has anybody else run into this problem?
I have the same problem you are having...unable to map a drive from any computer in my home. More frustrating for me is that I have "two" DNS-343 boxes. One works just fine (maps each time) but not the other one. 
Don't bother factory reset and re-create the RAID5 as a D-Link technician asked me to. I wasted 10 days backing up my data. Flushing DNS and WINS didn't help. 
I'm now wondering if "two" DNS-343 can co-exist on the same network. Still waiting for answers. Anyone has a link where I can download firmware 1.01? My box used to work beautifully for more than three months until the upgrade to 1.03 b60. Thanks.