An unexpected error has occurred

‚ÄčThe "unexpected error" crops up a lot, unfortunately.

Unexpected error has occurred
There are quite a few service applications that have underlying services in Services on Server. I recommend that you make sure that the service is started before attempting to provision the service application. Notable examples are the User Profile Service Application and the Managed Metadata Service Application. Doing things in the wrong order usually results in this rather unhelpful error message when you try to go to the management page of your new service application.

In some cases the damage is not easily undone and it may be necessary to remove and then re-provision the service application. However it is always worth trying the SharePoint equivalent of a sharp blow to the side of the equipment cabinet; IISRESET.