In the "Media" section of Umbraco, right clicking on a node and
clicking "Create" results in the following error:

How to Fix:
- First, navigate here: "~umbraco\config\create" (Where the
tilde: that is the "~" symbol, represents your root
url)
- Open up "UI.xml" in your favourite text
editor
- Find the "nodetype" element with alias="media" - it
should look like this: <nodeType alias="media">
- Change the alias from "media" to "Media" (Note the
case sensitive upper case "M") - it should now look
like this: <nodeType alias="media">
- Save your changes
- Refresh the page and re-try right clicking on a node and
clicking "Create".
And there you have it! It should work perfectly now. Note - you
may have to make these changes again in the future when upgrading
your version of umbraco so it might be a good idea to keep a note
of this tutorial link somewhere on your computer.