I just tried to reproduce the issue with installing a new 5.1 host and updating it to the latest patch. For the DNS server I used IP addresses which are currently not in use. However, the datastore showed up without issues before and after patching the host.
I'd suggest you open a support call with VMware to find out what's causing the issue, i.e. whether it is an issue with your specific hardware/configuration or whether something went wrong with the patch.
André