When trying to open a virtual machine's console via the vSphere web client, I was receiving a fingerprint mismatch.
Cause: There was an existing DNS entry with the same name as the vCenter appliance.
The vSphere web console uses DNS to connect back to vCenter. Ensure there is a DNS entry for your vCenter that matches the hostname of the vCenter server.
Note: This will be more common with the vCenter appliance, but may also impact vCenter installable.