Document Copy doesn't work

I log myself as an admin or a superadmin in one of my subwikis, I go to the sandbox space index.
For the document TestPage1 I click on the link "Copy", I get the page:
CopyDocument?sourcedoc=rtemplate%3ASandbox.TestPage1
where the field Source Document is already filled with "rtemplate:Sandbox.TestPage1"

I enter "rtemplate:Sandbox.TestPage_essai" for Target Document and click on Copy.
This line appears :Copying document rtemplate:rtemplate:Sandbox.TestPage1 ? to rtemplate:rtemplate:Sandbox.TestPage_essai?
and (obviously) my page is not created.

So I try again with these parameters: Sandbox.TestPage1 for source document and Sandbox.TestPage_essai for target document.
I click on copy.

I get these line:
Copying document rtemplate:Sandbox.TestPage1 to rtemplate:Sandbox.TestPage_essai?
(And my page is still not created.)
So even if it found my source document, it could'nt create my target document.