Hi Garry Clark,
Thank you for reporting this issue.
We are now aware of it the bug and have logged it for fixing. Unfortunately I can not give you a specific time frame for when the fix will be available. As a temporary workaround you can select the parent of the hidden page, and then in the text box just type in the rest of the URL.
I have updated your account. If you have more issues/concerns, please feel free to contact us.
the Telerik team