vCenter Appliance - Server (vpxd) will not start

I am running the Linux-based vCenter appliance version 5.1.0.10100 Build 1123965 and am using the embedded database.  As of this morning, I can no longer connect to the server with the vi client.  The web GUI responds on port 5480 and the "Summary" shows that the "Server" is "stopped".  Clicking "start" does not change the Server status.

I logged into the appliance and tried starting the vmware-vpxd service manually and I get a "failed" status.  I looked at the vpxd.log file and am receiving the following error:

Failed to connect to database : ODBC error: (08001) - [unixODBC] could not connect to server: Connection refused. (See attached image)

Using the web GUI, I tried the "Test Settings" button on the database page and I receive an error "Incompatible DB schema version" (See attached image)

I tried the steps in this article: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2035070  This procedure fails with the same error "Incompatible DB schema version". (See attached image)

This problem happened once before where the Server service showed "stopped" in the web GUI, but a reboot of the appliance fixed the problem.  This time a reboot did not work.

Nothing has changed on this server and it was working fine when I left the office on Friday.  Any ideas on what's going on here and how to fix it?

Thanks in advance for your assistance!
ODBC-Error.jpg
Web-GUI-Schema-Error.jpg
vpxd-start-error.jpg