Can't use Remote Console in Web Client: "SSL verification failure for 'My_ESXI_Host' due to a host thumbprint mismatch: stored thumbprint does not match certificate thumbprint."

I'm brand new to vSphere 5.5.  I just upgraded a 4.1U1 install and everything went well.  However, now that I'm trying to work with the web client, I can't actually connect to any of my VMs via the Launch Console functionality.  It spawns a new browser window and then gives me the error shown in the topic about a SSL cert thumbprint mismatch.  My Google-fu showed a VMware KB article about stopping the Web Client service an then going into %ProgramData%\VMware\vSphere Web Client\SerenityDB\ to delete whatever's there and restart the service - no effect.

Any clues?  I can still connect without issue using the standard 5.5 vi-client.